pet·ro·my·zon \ˌpe.trōˈmīˌzän\noun Etymology: New Latin Petromyzont-, Petromyzon, from petr- + -myzont-, -myzon -myzon 1.capitalized: a genus (the type of the family Petromyzontidae) of cyclostomes comprising the typical lampreys 2.-s: any cyclostome of the genus Petromyzon