Green’s Dictionary of Slang

1. (US campus) to become angry.

1975		G. Underwood ‘Razorback Sl.’ in AS L:1/2 61: horns, growv phr Become angry.
1997		C. Hiaasen Lucky You 221: Don’t get stupid, he warned himself. It’s no time to grow horns.

2. see under horns n.