An onomatopoeical adjective based on the sound emitted when something is "oh so tasty" (either through hunger or flavorological value) that one gnaws through it without regard to cleanliness or etiquette. This sort of ravenous eating will often result in an "om nom nom nom" noise being emitted from the eater.
Arthur: Gosh, I haven't eaten for days.
Dirk: Me neither. We're both starving equally.
Arthur: Look! A whole cooked chicken with side of mashed potatoes and a warm/soft dinner roll!
Dirk: We have to decide which of us gets to eat first. To be fair, we should rock-paper-scissors for it.
Arthur: Om nom nom nom nom!
Dirk: Arthur, you're a jerk. A real knee-biter.
by Tom and Jana December 19, 2004
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.
Cookie Monster: "COOOKIES!!!!!! OM NOM NOM NOM" (Eats everything, including plate)
by Hollis X April 10, 2008
The act of eating in a vigorous manner
As soon as Eric got his food he om nom-ed it so fast
by mri20one December 24, 2007
Exclaimed by various users on the website ProTrade when a delicious new floor shortable stock appears.
CW: Hey, Phil Hughes isn't on the Yankees 40 man roster and tomorrow is September 1st.

by College Wolf September 1, 2008
the sound one makes when eating and wants to make everyone around them annoyed and desires to be obnoxious.
Mom: bob! eat your peas!
Bob: fine (eats a forkfull of peas)
Bob: om nom om nom
Mom: (gives bob the evil eye) bob!
Mom: Bob!
Bob: om nom om nom
Mom: one!
Bob: om nom om nom
Mom: two!
Bob: om nom om nom
Mom: three!!!!
Bob: om nom o-
(mom drags bob out by the ear and throws him in the trash)
(two seconds later the garbage truck goes by and takes bob)
by 500kit500 March 9, 2017
To make out with someone without the tongue. Much more enjoyable because tongues are nasty bacteria-filled sponges that get in the way when kissing passionately.
Because she didn't like making out with tongue, she and her boyfriend we om nomming to make it more enjoyable.
by heygirlheyradical April 9, 2012