semilunar valve /-lo̅o̅″nər/ [L, semi + luna, moon, valva, folding door] , 1. a valve with half-moon–shaped cusps, such as the aortic valve and the pulmonary valve. 2. any one of the cusps constituting such a valve. 3. simple cuplike valves found in the venous and lymphatic vessels. See also heart valve, mitral valve, tricuspid valve.
