When having a girl bent over and fucking her in the pussy you shove your thumb in her ass and hook it so you can hold on and she can't get away.
I thumb locked my girlfriend and she loved it.
by joemomma69 March 25, 2011
a greco-roman wrestling move, originating from southwest florida, in which one grappler penetrates the other's asspipe with his thumb
throw in the thumblock!!
by Chuck Blonde December 12, 2007