1 definition by YousaywhyIsaywhynot
Commonly used term orginating in the early 1900s, when it was legal for men to beat their wives, as long as they used a stick no wider than their thumb.
Rule of thumb? Can't do too much damage with that thing, can we? Perhaps it should have been the Rule of Wrist. - The Boondock Saints
by YousaywhyIsaywhynot October 23, 2006