informal, offensive an obnoxious or despicable person
2.
informal, jocularoften a person, esp a man: lucky bastard
3.
informal something extremely difficult or unpleasant: that job is a real bastard
4.
old-fashioned, offensiveor a person born of unmarried parents; an illegitimate baby, child, or adult
5.
something irregular, abnormal, or inferior
6.
a hybrid, esp an accidental or inferior one
—adj
7.
old-fashioned, offensiveor illegitimate by birth
8.
irregular, abnormal, or inferior in shape, size, or appearance
9.
resembling a specified thing, but not actually being such: a bastard cedar
10.
counterfeit; spurious
[C13: from Old French bastart, perhaps from bast in the phrase fils de bast son of the packsaddle (that is, of an unlawful and not the marriage bed), from Medieval Latin bastum packsaddle, of uncertain origin]