/ ˈbɑːstəd; ˈbæs-; NAmE ˈbæstərd/ noun
1.
( taboo , slang ) used to insult sb, especially a man, who has been rude, unpleasant or cruel :
He's a real bastard.
You bastard! You've made her cry.
2.
( BrE , slang ) a word that some people use about or to sb, especially a man, who they feel very jealous of or sorry for :
What a lucky bastard!
You poor bastard!
3.
( BrE , slang ) used about sth that causes difficulties or problems :
It's a bastard of a problem.
4.
( old-fashioned , disapproving ) a person whose parents were not married to each other when he or she was born
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WORD ORIGIN
Middle English : via Old French from medieval Latin bastardus , probably from bastum packsaddle, a horse's saddle used to support loads; compare with Old French fils de bast , literally packsaddle son (i.e. the son of a mule driver who uses a packsaddle for a pillow and is gone by morning).