The Collaborative International Dictionary of English v.0.48:

Sesamoid \Ses"a*moid\, n. (Anat.)
   A sesamoid bone or cartilage.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sesamoid \Ses"a*moid\, a. [Gr. ???? like sesame; ????? sesame +
   e'i^dos form: cf. F. s['e]samo["i]de.]
   1. Resembling in shape the seeds of sesame.
      [1913 Webster]

   2. (Anat.) Of or pertaining to the sesamoid bones or
      cartilages; sesamoidal.
      [1913 Webster]

   Sesamoid bones, Sesamoid cartilages (Anat.), small bones
      or cartilages formed in tendons, like the patella and
      pisiform in man.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sesamoid
    n 1: any of several small round bones formed in a tendon where
         it passes over a joint [syn: sesamoid bone, sesamoid,
         os sesamoideum]