Ponderous means slow, clumsy because of great weight. Dull, laborious, or solemn. His footsteps up the staircase were heavy and ponderous.

Well I think so Brain, NARF! But wouldn't that mean I would have to know what pondering means?

Poi Dog Pondering was created in 1985.

I was pondering what the future would hold, when my thoughts were interrupted.

Pretty close. Wondering has to have a specific object that you are wondering about. Pondering usually does too, but one could ponder generally without pondering about something.