(slang) A man who sells his body for money; a male prostitute.
(slang) A promiscuous man who has no regard for his sexual partners or the emotional value of his relationships.
Though Wikipedia also says: (for "bitch")
Its original use as a vulgarism, documented to the fourteenth century, suggested high sexual desire in a woman, comparable to a dog in heat. The range of meanings has expanded in modern usage.
In most general sense, "bastard" can be an equivalent. As in "You bastard!" versus "You bitch!". But there can still be different senses between them. It depends on the situation.
There is even the term "man bitch" according to urbandictionary.
A man that acts like a bitch. Malicious, unpleasant selfish person; especially like a woman. Weak or comtemptible.