Any kind of food, chow, eats, sustenance, etc., but particulary of the delicious snack variety.
May be colloquially referred to simply as "oms".
Bob: I'm really hungry man.
Billy: Let's book it to the 7-Eleven to get some omnoms then.
Joe: These bbq kettle chips are fucking delicious.
Susie: I know, they're my fave type of oms.