def.

def. (plural defs.)

1. Abbreviation of definition.

   Synonym: def

   • 2004, David Foster Wallace, “Twenty-Four Word Notes”, in Both Flesh and Not, New York, N.Y., Boston, M.A., London: Little, Brown and Company, published 2012, →ISBN, page 274:

     Lots of writers, though, think fervent is synonymous with fervid, and most dictionary defs. don't do much to disabuse them.