a legitimate or likely object of attack, mockery, etc.: With his fat, round face, the politician was fair game for the cartoonists.
Origin of fair game
First recorded in 1795–1805
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a legitimate object for ridicule or attack
hunting archaic quarry that may legitimately be pursued according to the rules of a particular sport
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
A legitimate target for attack or ridicule. For example, On his talk show, authors are considered fair game. This expression alludes to hunting. [Early 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.