Planaria \Pla*na"ri*a\, n.; pl. L. Planari[ae], E. -rias. [NL. See Planary.]

(Zo["o]l.) Any species of turbellarian worms belonging to Planaria, and many allied genera. The body is usually flat, thin, and smooth. Some species, in warm countries, are terrestrial.

Source: Webster's Revised Unabridged Dictionary (1913)