Meaning of semilunar valve

sem'ilu'nar valve'

Pronunciation: [key]
— Anat. Anat.
  1. either of two valves, one in the aorta and one in the pulmonary artery, consisting of a set of three crescent-shaped flaps of tissue and serving to prevent blood from flowing back into the heart after contraction. Cf.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.