a.)a term given to women with a perfectly round, bubble ass. (NOUN)
b.)when a beautiful slender woman has a beautiful round ass and smothers a guys face with it. (VERB)
a.)As soon as I stepped in to the club I saw a great profile of Susans ass. "man, want a winthrop", I said.
b.)I was dating this girl with the greatest ass I'd ever seen, and she would winthrop me all the time.