- noun the drug P.C.P. A powdered (usually home-made) version of an animal tranquilliser which is smoked or sniffed through a tube and which produces in the user unpredictable and extreme physical and psychological effects. Users are capable of acts of violence, hallucinations and periods of imperviousness to pain and superhuman strength. P.C.P. is easy to produce in home laboratories and became a severe social problem in US cities after 1975, principally among poorer teenagers. Fears of its spread to Britain and elsewhere were groundless. Its milieu is now largely given over to crack.