Source : Webster's Revised Unabridged Dictionary (1913)

Navus \Na"vus\, n.; pl.{N[ae]vi} (-v[=i]). [L.] (Med.)
   A spot or mark on the skin of children when born; a
   birthmark; -- usually applied to vascular tumors, i. e.,
   those consisting mainly of blood vessels, as dilated
   arteries, veins, or capillaries.