A sacred vow more powerful then a pinky promise. If it is a girl who broke said thumb promise she is intitled to 40 hours of oral sex upon the person who had the promise brokded. If its between two guys you must chop off either of your nuts for punishment.
by Hello kitty 69 May 08, 2008
A Thumb Promise is a promise stronger than a pinky promise. It shall never be broken, and if so, then the person who broke it may never be trusted again. Crossing your fingers does not invalidate a thumb promise.
by syylent June 08, 2024