The Collaborative International Dictionary of English v.0.48:

Tricuspid \Tri*cus"pid\, a. [L. tricuspis, -idis; tri- (see
   Tri-) + cuspis a point: cf. F. tricuspide.]
   1. Having three cusps, or points; tricuspidate; as, a
      tricuspid molar.
      [1913 Webster]

   2. (Anat.) Of or pertaining to the tricuspid valves; as,
      tricuspid obstruction.
      [1913 Webster]

   Tricuspid valve (Anat.), the valve, consisting of three
      triangular membranous flaps, at the opening of the right
      auricle into the right ventricle in the heart of most
      mammals; -- sometimes called the tricuspid valves, each
      flap being regarded as a valve.
      [1913 Webster]

WordNet (r) 3.0 (2006):

tricuspid valve
    n 1: valve with three cusps; situated between the right atrium
         and the right ventricle; allows blood to pass from atrium
         to ventricle and closes to prevent backflow when the
         ventricle contracts [syn: tricuspid valve, right
         atrioventricular valve]