What is the meaning of Hmm?

ISO 639-3 language code for Central Mashan Hmong.

Indicates thinking or pondering.

Indicates surprise or cluelessness; especially a response by a person who is questioned or addressed when not expecting it.

A demand for an answer to a question.

To make a thoughtful humming noise.

hmm

expressing skepticism

Indicating thinking, pondering, surprise or annoyance.

hmm (indicating thinking or pondering)

alternative form of hm

Source: wiktionary.org