Someone who is good-natured or amiable under circumstances that are unpleasant or not ideal. I know you're disappointed to have lost the game, but try to be a good sport, OK? Thankfully, they were good sports about all our teasing.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
(a) good sport
someone who can accept a loss in a competition or can accept being the butt of a joke. Bob is usually a good sport, but this time he didn't seem to appreciate your joke.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.