Pleurotoma \Pleu*rot"o*ma\, n.; pl. L. {Pleurotom[ae]}, E. {Pleurotomas}. [NL., fr. Gr. ? the side + tomh` a cut.] (Zool.) Any marine gastropod belonging to {Pleurotoma}, and ether allied genera of the family {Pleurotmid[ae]}. The species are very numerous, especially in tropical seas. The outer lip has usually a posterior notch or slit. [1913 Webster]