Definitions

1. noun

A person with a gruff or unpleasant manner, especially one who is considered to be a bit of a bully or a thug.

“He was known as a crackjaw in the neighborhood, and nobody wanted to mess with him.”

2. noun

A person who is a bit of a troublemaker or a ruffian.

“The crackjaw in the group was always causing trouble and getting into fights.”