Definition of "thwack" [thwack]

• To strike or hit with a flat object; whack. (verb-transitive)
• A hard blow with a flat object; a whack. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "What they forgot to take into account, however, is that you do not hear the primary charge of a rifle being fired if you are more than 100 metres from it, you only hear the "thwack" or "crack" of the bullet passing overhead, followed by a MUTED primary charge thump (weapon firing)."
• "A good meaty "thwack" means the thrower needs to go hide for a few seconds."
• "At the last moment she turned parallel to the chukar's line of flight and hit it from behind with the solid "thwack" of a large-caliber bullet striking flesh."