The word Hmmf is generally used within friendships when a particular friend is in a bad mood, or in a 'hmmf' with the other.
Susan was in a hmmf because her friend Carol was spending all her time with her boyfriend.
Carol: Susan, are you in a hmmf with me?
Carol: Are you sure?
Susan: YES! I AM SURE OK!??!
Carol: Your deffinatly in a hmmf.