A jokingly derogatory term Aggies use for Bevo, the longhorn mascot of the University of Texas. Indicates that the creature (and the school, by extension) is of exceptionally poor quality and is only
fit to be ground-up and served as taco meat.
This term became especially
popular after an ESPNU commercial depicting an Aggie playing a Pictionary/charades-like
game. The visual prompt included
UT's longhorn logo and a hook. The aggie refused to answer "Hook '
em Horns" and instead refers to the longhorn (somewhat disgustedly) as taco meat.
The video can be found online quite easily.