Green’s Dictionary of Slang

air biscuit n.

an extremely malodorous fart or belch.

[US]Dly Tar Heel (Chapel Hill, NC) 7 Feb. 3/2: Hell, we like to fart [...] There are specific places around campus that make for classic air biscuits.
[US]T. Dorsey Florida Roadkill 193: The passenger looked up from his gun parts, apologetic. ‘Air biscuit’ [...] All three rolled down their electric windows.
OnLine Dict. of Playground Sl. [Internet] air biscuit n. the ‘aromatic’ result of breaking wind.
[US]News Jrnl (Wilmington, DE) 14 Nov. F4/4: When gas heads south — usually called a fart, an air biscuit or a toot [etc].
[US]Dly Jrnl Franklin, IN) 5 Oct. A6/3: She’s a gassy dog to begin with. Sliders mised with regular doggy air biscuits would be disastrous.

In phrases

float an air biscuit (v.)

1. to break wind; to burp.

[US]Santa Cruz Sentinel (CA) 9 Sept. D1/4: Chase and Goldberg bantered about some star who floated an ‘air biscuit’ and stunk up a studio.
[UK]Roger’s Profanisaurus in Viz 87 Dec. n.p.: float an air biscuit euph. To release a fart.
[US]Palm Beach Post 26 Sept. 3D: You’re supposed to keep track of how many times you float an air biscuit.
[US]Tallahassee Democrat (Tallahassee, FL) 19 Feb. D3/3: Obviously, Mr. Kunkel has never had the privilege of sharing the couch with Shuggie Pop, our younger Russian Blue, when he decides to float an air biscuit and clear the room.

2. (US campus) to vomit.

[US]Eble Campus Sl. Spring 1: blow cookies – vomit. Also earl, float an air biscuit.