The Collaborative International Dictionary of English v.0.48:

Jell-O \Jell"-O\, jello \jell"o\n. [a trademark.]
   a brand of sweetened fruit-flavored powdered mixture,
   packaged so that it can be conveniently dissolved in hot
   water and solidified into a gelatin, used as a dessert,
   sometimes with pieces of fruit mixed in; also the gelatin
   dessert thus prepared; sometimes used metaphorically; as,
   when he pulled a gun on me, my knees turned to Jell-O..
   [Trademark]

   Note: Jell-O was originally a trademark and is still
         protected by trademark law, but is often used as one
         word, uncapitalized in informal writing.
         [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

jello
    n 1: fruit-flavored dessert (trade mark Jell-O) made from a
         commercially prepared gelatin powder [syn: jello,
         Jell-O]

The Jargon File (version 4.4.7, 29 Dec 2003):

jello
 n.

    [Usenet: by analogy with spam] A message that is both excessively
    cross-posted and too frequently posted, as opposed to spam (which is
    merely too frequently posted) or velveeta (which is merely excessively
    cross-posted). This term is widely recognized but not commonly used; most
    people refer to both kinds of abuse or their combination as spam.