1. n. a despicable person, usually a male. (Euphemistic for son of a bitch.) If that son of a gun thinks he can boss me around like that, he’s got another think coming.
2. n. old buddy. I went to school with this son of a gun! He’s my old buddy.
3. exclam. I am totally surprised!; I am shocked! (Usually Son of a gun!) The thing just blew up! Son of a gun!