Wiktionary
n. A psychoactive drug taken deliberately for the effect it has on the mind rather than for its medicinal effects.
WordNet
n. a narcotic drug that is used only occasionally and is claimed to be nonaddictive
Usage examples of "recreational drug".
The couples, for example, were recreational drug users and had met up with a dealer selling some new and pernicious designer drug that could not be detected through routine toxicology tests.
The ostensible point is to punish recreational drug consumers for their role in the nation's hellish narcotics problem.
Ten years later Sernyl would be known primarily by its street names - hog, crystal, DOA, angel dust, PCP - and emerge as the main recreational drug of the inner-city ghettos.
A surprising number of the women who had been his lovers were recreational drug users, and over the past couple years, he had met several dealers who supplied them.
I think that the phrase 'recreational drug' is extraordinarily pernicious.