Green’s Dictionary of Slang

disco n.

SE in slang uses

In compounds

disco biscuit (n.) (also disco burger) [its shape and the environment in which it is often consumed]

1. one who frequents discotheques.

Texas Mthly Nov. 155: If it wasn't for me, there would be no Gilley's, there would be no Urban Cowboy, and Travolta would still be some kind of disco biscuit.
Sassy n.d. 221/3: That song is you at your disco biscuit best.

2. a Qualuude (methaqualone).

[US]Newsweek 28 Sept. 93/1: They prescribe a bottle of Quaaludes, a powerful and popular sedative known technically as methaqualone—and to legions of abusers as ‘pillows’, ‘disco biscuits’ and ‘vitamin Q’ .
G. Cagle Payola! 50: ‘Lude, vitamin Q, disco biscuit, gorilla pill [...] When it comes to drugs, I'm just a precious novice’.

3. (drugs) MDMA.

P.J. O’Rourke Parliament of Whores 118: Who wouldn’t rather have a couple of plump, flaky lines on a mirror and half a disco biscuit than lead the lives these people are leading?
[UK]S. Champion Disco Biscuits v: Dennis The Menaces, Rhubarb and Custards, White Callies, Pink Flamingoes, Snowballs, Kinder Eggs, Energizers, Hammer & Sickles, Disco Biscuits.
[UK]K. Waterhouse Soho 51: Not that Alex had ever done drugs, apart from Es or disco biscuits as they were known.
London NHS Trust Community Drug Service ‘The Facts About Ecstasy’, In the Limelight 🌐 What is ecstasy? [...] It is also called E, XTC, Adam, Love Doves, New Yorkers, M25’s, Disco Burgers, Dennis The Menace to name a few.
[Aus]R.G. Barrett Mystery Bay Blues 26: Just because I drop the odd disco biscuit and hit a rave now and again [...] doesn’t mean I don’t like [...] rock ’n’ roll.
disco danny (n.)

(US) a male fan and frequenter of nightclubs.

[US]C. Hiaasen Skin Tight 82: In contrast to the disco Dannies, the mates wore T-shirts and sandals and deep Gulf Stream tans.
disco powder (n.)

amphetamine sulphate.

[UK]N. Barlay Crumple Zone 34: Checks me out first like a bint asking him for a wrap of disco powder up the Plastic Coconut in Tottenham.