NOUN (3)

1. an amateur boxer who weighs no more than 165 pounds;

2. a wrestler who weighs 172-192 pounds;

3. a professional boxer who weighs between 155 and 160 pounds;

WordNet (r) 3.0 (2006):

middleweight
    n 1: an amateur boxer who weighs no more than 165 pounds
    2: a wrestler who weighs 172-192 pounds
    3: a professional boxer who weighs between 155 and 160 pounds

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "middleweight":
   Chinese boxer, bantamweight, black belt, boxer, brown belt,
   bruiser, catchweight, featherweight, fighter, fisticuffer,
   flyweight, heavyweight, karate expert, light heavyweight,
   lightweight, palooka, prizefighter, pug, pugilist, savate expert,
   sparrer, welterweight