Green’s Dictionary of Slang

(US campus) to vomit.

1971		Current Sl. V:4.
1982		W. Safire What’s The Good Word? 304: If I do too much brew, I’ll get wicked-faced, boot, and maybe even pass.
1997–2001		Online Sl. Dict. 🌐 boot v 1. to vomit (‘I booted last night.’).
2001		Eble Campus Sl. Fall 2: BOOT – Vomit.