pl. sons of guns . Slang.
1. rogue; rascal; scoundrel: That son of a gun still owes me $20.
2. a tiresome or disagreeable matter, chore, etc.
3. (used as an affectionate greeting, term of address, etc.): Charlie Humpelmeyer, you old son of a gun, how are you?
4. (used as an exclamation of irritation, surprise, dismay, etc.).
[ 1700-10; perh. orig. the illegitimate offspring of a soldier, though later influenced by Brit. argot gun thief; cf. GUN MOLL ]