The Collaborative International Dictionary of English v.0.48:
hard-bitten \hard-bitten\ hard-boiled \hard-boiled\adj. not given to sentimentality or gentleness; -- of people; as, a hard-bitten character. Syn: pugnacious, tough. [WordNet 1.5 +PJC]WordNet (r) 3.0 (2006):
hard-bitten adj 1: tough and callous by virtue of experience [syn: hard- bitten, hard-boiled, pugnacious]