1. Term used to describe an indescribable item, idea, thought, or action.
2. Also used to say or reply with in an awkward/uninteresting/unpleasant conversation when you literally have nothing else to say.
3. This word actually has no meaning whatsoever.
Mary: "I can't wait for the new Justin Bieber album to come out, like it's gonna be amazing, my life will officially be complete, omggg <3"
Carlos: "Humdeem."
The act of masturbating onto someone's face at the same time as having your testicles hummed on by another person, while you are all in a twelve-man camping tent and the other nine people are asleep.
Dude, you won't believe what I did on our yearly camping trip last night! I gave a chick a Hogpen Humdinger!!!