son of a bitch

A person regarded as thoroughly mean or disagreeable.

Used to express annoyance, disgust, disappointment, or amazement.

Also, SOB; son of a gun. A mean, disagreeable individual, as in He was regarded as the worst son of a bitch in the industry, or He ran out on her? What an SOB, or He's a real son of a gun when it comes to owing you money. The first of these terms, calling a man the son of a female dog, dates from the early 1300s and is considered vulgar enough to have given rise to the two variants, both euphemisms. The first variant, an abbreviation, dates from World War I. The second, first recorded in 1708, gave rise to the theory that it originally applied to baby boys born at sea (in the days when women accompanied their husbands on long voyages). The explanation seems unlikely, especially since presumably some of the babies were girls. It also once meant the illegitimate son of a soldier (or "gun"). More probably, however, son of a gun evolved simply as a euphemism for the first term and appealed because of its rhyme. Both it and son of a bitch are also put as interjections expressing surprise, amazement, disgust, or disappointment, as in Son of a bitch! I lost my ticket, or I'll be a son of a gun! That must be the governor.

The noun has one meaning:

Meaning #1: (obscene) insulting terms of address for people who are stupid or irritating or ridiculous
  Synonyms: asshole, bastard, cocksucker, dickhead, shit, mother fucker, motherfucker, prick, SOB