Definition of "hmm"

hmm

/hm̩/

interjection
1. Indicating thinking or pondering.
  Quotations
  Jeeves: Foreign travel often liberates emotions best kept in check, sir. The air of North America is notoriously stimulating in this regard, as witness the regrettable behavior of its inhabitants in 1776.B. Wooster: Hmm? What happened in 1776, Jeeves?Jeeves: I prefer not to dwell on it, if it's convenient to you, sir.
  May 12 1991, “Kidnapped!”, in Jeeves and Wooster, season 2, episode 5
2. A demand for an answer to a question.
verb
third-person singular simple present hmms, present participle hmming, simple past and past participle hmmed
1. (intransitive) To make a thoughtful humming noise.