Green’s Dictionary of Slang

1. (US campus) very drunk.

1975

G. Underwood ‘Razorback Sl.’ in AS L:1/2 68: He got vegetable on beer.

2. brainless, very stupid.

1979		J. Morrow Confessions of Proinsias O’Toole 37: A squat negro had gutter-fought him for eleven rounds and, with a head butt in the 12th, had sent him to the vegetable ward for six months.
1997		N. Barlay Curvy Lovebox 138: Two vegetable kids peerin’ into nowhere.