sheep dip 
noun [mass noun]
1A liquid preparation used to rid sheep of external parasites.Everybody needs to be aware of the effects organophosphates used in pesticides and sheep dip can have on people's health....
- A good Wensleydale coat is not as simple as a good cut - there are plenty of closely guarded methods of achieving perfection - hardness of water, composition of sheep dip.
- He says the black market in organophosphates sprang up following the ban on such chemicals being used in sheep dip.
1.1 [count noun] A trough or similar container in which sheep are immersed in sheep dip.