We don't have synonyms for porkpie hats yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are porkpie hat and pork pie hat.
(n) :
Alternative spelling of pork pie hat. [A flat-topped, round, man's hat popular among musicians of jazz, blues, and ska, made famous by the actor Buster Keaton and the jazz musician Lester Young.]
(n) :
Alternative spelling of pork pie hat. [A flat-topped, round, man's hat popular among musicians of jazz, blues, and ska, made famous by the actor Buster Keaton and the jazz musician Lester Young.]