Entry 1 sense Webster, 1913 Lacertus /(lȧ*sẽr"tŭs)/ · La·cer·tus · IPA /ləˈsɝː.təs/ 01 n. A bundle or fascicle of muscular fibers. pl. Lacerti ((-tī)) 1. A bundle or fascicle of muscular fibers.(Anat.)