Originally: any of various large extinct marine reptiles of the former order Pythonomorpha (corresponding to the present-day suborder Mosasauria); a mosasaur; (now disused). Now: any reptile of the clade Pythonomorpha, which comprises the mosasaurs together with modern snakes.
Of or relating to the order or clade Pythonomorpha.
Mid 19th century; earliest use found in Edward Cope (1840–1897). From scientific Latin Python + -o- + -morph, after scientific Latin Pythonomorpha, former order name.