The sound you make/words you say when you imagine/think about one of two things:

  1. a particularly sumptuous article of food,

  2. or

  3. getting some action with a particularly hot and sexy individual.

Or just a general phrase to use when you are at a loss--not so much in an awkward situation but just bored or semi-retarded. Also pronounced "humina humina", and may be substituted for "hubba hubba" depending on the context and situation.