MMM (pronounced similar to Ermm or Umm) is an interjection commonly used in English as an "Expression of Pleasure or Contentment." In text-based messaging, MMM is often used to show pleasure at something that someone has just typed.

Is MMM in the dictionary?

Yes, mmm is in the scrabble dictionary.

What kind of word is mmmm?

An expression used to show contentment for something. "mmm this is a tasty pie!" An expression used to show thought or reflection.