Mystery Moose is the act of making a moose sound (and hand gesture on side of head) whilst performing a sexual act on a partner in the 'doggy style' position.
He was banging me from behind and I heard a strange moose sound, I asked him what this was and he said he couldn't hear it, I heard it again and again and he still said nothing. A short time later he started laughing to himself and revealed it was him making the sound, aka, Mystery Moose.
by Callum Reckless December 04, 2008
Can you define these popular missing words?