The Collaborative International Dictionary of English v.0.48:

Jell \Jell\, v. i.
   1. To jelly. [Colloq.]
      [1913 Webster]

   2. To take on a more concrete or substantial form; -- of
      ideas, plans, programs, etc.
      [PJC]

WordNet (r) 3.0 (2006):

jell
    v 1: become gelatinous; "the liquid jelled after we added the
         enzyme" [syn: jell, set, congeal]