Definition of disco biscuit in US English:

disco biscuit

noun

British
informal
  • A tablet of the drug Ecstasy.

    • ‘From Hasselhoffs to disco biscuits, a leading doctor has lifted the lid on the colourful slang used by staff on Britain's hospital wards.’
    • ‘I'd heard about Doves, Disco Biscuits and these micro-dots of acid that came on cardboard pucks.’
    • ‘What's worse is that even though the new disco biscuit of choice has a sexy name, it's still essentially speed.’
    • ‘I mean you trusted that Ambulance officer when you lapsed into unconsciousness after doing too many disco biscuits.’
    • ‘They brought not only "Da ruckus" but armfuls of club bangers, disco biscuits and 'one size fits all' gold hot pants for everyone.’
    • ‘We came upon a sixty-something lady out in her front garden with her poodle running around like a dance club diva on disco biscuits.’
    • ‘The table at first glance seems to give the impression that almost half of the youth population takes a disco biscuit once or twice a year.’
    • ‘Sooner or later he will ask you if you want any disco biscuits.’
    • ‘You'd have to seriously ask what sort of disco biscuits the girls' parents were doing in 1985.’
    • ‘Her husband presented her with a bag of Quaaludes, a popular 1970s drug sometimes known as "disco biscuits".’

Origin

1980s (in the US sense ‘tablet of Quaalude’): from disco + biscuit.