A fun phrase to say when somebody is eating something, the original usage of this word began as "nom nom nom" and was largely used online for lawlcats and the like. After the popularity of "dot com" in song and web, the dot com was added largely because it rhymed.

The sound of ravenous eating. Popularized by the character Cookie Monster on Sesame street, it is now used commonly in speech, especially among younger people. Cookie Monster exclaims "OM NOM NOM NOM" when gobbling down cookies (and whatever else goes in his mouth).

You can "om nom" on things besides food... for example, play-eating babies' toes to make them laugh.

omnomnomnom (dot) com is a pop culture website where people submit their own silly photos that have been manipulated in Paint to resemble monsters eating various things, including people and pets.