1) the phrase often used as a sound to describe the noise a person makes when they eat
2) an awkward silence filler
3) used by nerdy teenage girls
person eating kebab: UMNUMNUMNUMNUM
me: stfu, you eat like a freakin fatass
person eating kebab: fuckin' yummeh kebab :]
teenage girl: umnumnum! tehe
Me: oh myy, you think you're so random but you're not.