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3.
On urbandictionary, a thumb war consists giving your own definition a thumbs up and giving a rival's definition a thumbs down on a daily basis while said rival does the same for himself. A thumb war is won when one of the contenders forgets to vote and/or gets a life.
I hope the addition of this definition doesn't provoke a thumb war.
by y=mx+b January 23, 2009
 
1.
Texting battle; Fighting through text messaages; Sending and receiving mean, nasty negative text messages back and forth with someone.
"Ashley and Derek were engaged in a nasty thumb war last night."

"Damn, that was a ugly thumb war!"

"You should see some of the outrageous things Caitlyn wrote to Carrie during their thumb war. She definitely won that one!"
by JacDod August 16, 2011
 
2.
A Game Where you cuff Your Hand and Your Enemys Hands into One, both Lifting Your Thumbs And say '1,2,3,4, i declare a thumb War!!'(maybe something other) and try to pin the enemys Thumb under yours. You may only use 1 hand. the winner who pins his enemys thumb down for a short time(5-10 seconds) wins the so called war.
Me And austin Had a thumb War last night, i totally owned him.
by Sythex June 18, 2007