WordNet sense 1 (a person who is gullible and easy to take advantage of):

chump, fool, mark, mug, patsy, sucker, fall guy, soft touch

WordNet sense 2 (make a fool or dupe of):

befool

WordNet sense 3 (mostly white aquatic bird having long pointed wings and short legs):

seagull

WordNet sense 4 (fool or hoax):

cod, dupe, slang, put on, take in, put one across, put one over