Definition of terms

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Name Description Related terms
objective sample

A sample of a food or other agricultural commodity taken at random.


Necessary, obliged.

obligate parasite

A parasite is an organism that can live only on living matter.

Opposite of 'facultative parasite'.

occasional pest

A pest generally under natural control that exceeds the economic injury level only sporadically or in localised areas.


From s. 3 of the Agvet Code and s. 3 of the Agricultural and Veterinary Chemical Products (Collection of Levy) Act 1994:

In relation to any premises or a part of any premises, means the person in occupation, charge or control of the premises or of that part of the premises, as the case may be.

octanol-water coefficient

A coefficient that provides a measure of the lipophilicity of a chemical (ie whether the chemical preferentially partitions into fat or lipid tissue).

off label use
off-label permit

A permit that allows specified registered agvet products to be used for a purpose or in a manner that is not included on the approved label.


Within 24 hours of shearing.

off-target spray
Office of Chemical Safety (OCS)

A liquid of high carbon and hydrogen content that is immiscible with water but soluble in alcohols or ethers and usually flammable; may be sourced from animal, plant or petroleum-based origins. Oils are commonly used to carry or dissolve an active constituent in a pesticide formulation, or for direct application as a pesticide.

oil based

Dissolved or formulated in an oil or similar petroleum fraction that is not soluble in water.

oil dispersion

A stable suspension of the active constituent(s) in water-miscible fluid, which may contain other dissolved active constituent(s), intended for dilution with water before use.

The APVMA formulation type code for an oil dispersion is OD.

oil phase

The non-aqueous liquid portion of an emulsion that consists of water-insoluble active constituents with or without surfactants or solvents.

oil-dispersible powder

A powder formulation to be applied as a suspension after dispersion in an organic liquid.

oil-miscible flowable concentrate (oil-miscible suspension)

A stable suspension of active constituent in a fluid intended for dilution in an organic liquid before use.

oil-miscible liquid

A liquid, homogeneous formulation to be applied as a homogeneous liquid after dilution in an organic liquid.

The APVMA formulation type code for oil-miscible liquid is OL.


Any of several seeds grown for the extraction of oil after harvest (eg cotton seed, sunflower seed, safflower seed, rape or canola seed, linseed, sesame seed).

oncogen, oncogenesis, oncogenic, oncogenicity

Terms that are complementary to the terms 'carcinogen', 'carcinogenesis', 'carcinogenic', 'carcinogenicity'. Oncogens produce any kind of tumour (ie malignant or benign). Carcinogens are connected with carcinomas (ie malignant tumours).

open sale

Preparations that may be bought without the presentation of a prescription.

operating speed

The constant rate at which a pesticide sprayer moves during application, usually measured in kilometres per hour (km/h) or metres per second (m/s)


A functioning unit of genomic DNA that contains a cluster or group of genes that is under the control of a single regulatory signal or promoter.

opportunity crop

The flexible cropping system in which more than one crop per year can be grown on the same land if soil moisture permits.


Of, or by, through or into the mouth.

oral toxicity

The adverse effects on an organism caused by a substance received through the oral route.

ordinal variable

An ordinal variable allows a ranked order in the items measured, in terms of which has less and which has more of the quality represented by the variable, but does not allow a quantification of how much more.

ordinal variables
ordinary office hours

From s. 3 of the Agvet Code:

Means the hours when the office of the APVMA is open to members of the public.

organic farming

A production system that avoids or largely excludes the use of synthetically compounded fertilisers, pesticides, growth regulators and livestock feed additives. To the maximum extent feasible, organic farming systems rely upon crop rotations, crop residues, animal manures, legumes, green manures, off-farm organic wastes, mechanical cultivation, mineral bearing rocks, and aspects of biological pest control to maintain soil productivity and tilth, to supply plant nutrients and to control insects, weeds and other pests.

organic matter

The humus or decomposed remains, in the soil, of plants and animals. Organic matter is the food of soil fungi and bacteria. Soils high in organic matter support large populations of microorganisms, plants and invertebrates.

organic pesticides

Pesticides that contain carbon. The two major groups of organic pesticides are petroleum oils and synthetic organic pesticides.

organic soil

A soil greater than 40 centimetres (cm) thickness and containing more than 30 per cent organic matter.

Organisation for Economic Co-operation and Development (OECD)

Established in 1961, the Organisation for Economic Co-operation and Development (OECD) brings together the governments of countries committed to democracy and the market economy from around the world to:

  • support sustainable economic growth
  • boost employment
  • raise living standards
  • maintain financial stability
  • assist other countries' economic development
  • contribute to growth in world trade.

The OECD also shares expertise and exchanges views with more than 100 other countries and economies, including the least developed countries in Africa. The OECD has initiated international cooperation for the safe use and management of agricultural chemicals through its pesticides and chemical management programs.


Any living thing (plant or animal).

organochlorine pesticide

Pesticides that have a relatively high proportion of organically bound chlorine (eg DDT, BHC, aldrin, dieldrin, endrin, heptachlor and lindane).


Pertaining to, or perceived by, a sensory organ.

Organophosphates or organophosphorus insecticides (OPs)

Insecticides that contain one or more phosphorus ester groups and which possess the ability to inhibit cholinesterase enzyme activity in all species of animals, including arthropods.

original container

The package (bag, can, bottle, etc.) prepared by the manufacturer in which an agvet chemical product is packed and sold.

ornamentals or ornamental plants

Plants that are used to beautify homes, gardens and lawns, including trees, shrubs and flowers, and not usually used as a source of food.

outer pack

The container in which an agvet chemical product and its inner pack are presented for sale. In the case of a bottle in a box, the bottle is the inner pack and the box is the outer pack.

over-the-top application (or overtop application)

An application methodology where a pesticide is applied over the top of transplanted or growing plants by an aeroplane, helicopter or raised spray boom on a ground rig. It is sometimes used more generally to describe a broadcast pesticide application above the plant canopy.


The excess of active constituent(s) deliberately added to a formulation to compensate for manufacturing loss or loss during storage.

overall spray

A spray applied uniformly over an entire area.


Usually two times the maximum concentration of an agvet chemical product, but it may be as high as 10 times in the case of live immunobiological products.

overseas holder

The portion of a powdered solid material, being particles or agglomerates, that is larger than a specified size.


A chemical that kills the eggs of insect, mites or nematodes.


Of, or pertaining to, sheep.

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