Sentence:  For many years Bud Abbott served brilliantly as Lou Costello's deadpan <WSD>straight man</WSD>. 
Meaning of the word marked with <WSD> tags:  A member (of any gender) of a team of comic performers who plays a supporting role by helping to set up jokes and punch lines through engaging in dialog with another comedian playing a more eccentric or otherwise more interesting character; a foil who plays such a role in theatrical comedy.