Green’s Dictionary of Slang

gassy n.

[gassy adj.1 (2)]

(US prison) a chatterer.

[US]G. Milburn ‘Convicts’ Jargon’ in AS VI:6 438: gassy, n. A talkative person.
[US]Goldin et al. DAUL 77/1: Gassy, n. A talkative person.