Definitions by Tysma

mmhmm 

a sound you make to express disinterest OR tremendous interest depending on the tone used

"Hey, check out my collection of bottle caps"
disinterested response: "mmhmm"
OR

"Hey check out my wifes new tits!!"

response: "MMMMMMMMMHMMMMMMMM"

mmhmm by Tysma July 1, 2008