The Collaborative International Dictionary of English v.0.48:

Thecodont \The"co*dont\, a. [Gr. ? a case + ?, ?, a tooth.]
   1. (Anat.) Having the teeth inserted in sockets in the
      alveoli of the jaws.
      [1913 Webster]

   2. (Paleon.) Of or pertaining to the thecodonts.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thecodont \The"co*dont\, n. (Paleon.)
   One of the Thecodontia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

thecodont
    n 1: presumably in the common ancestral line to dinosaurs and
         crocodiles and birds [syn: thecodont, thecodont
         reptile]