ponderous

Concise Oxford English Dictionary © 2008 Oxford University Press:
ponderous/ˈpɒndərəs/

▶adjective

• 1 slow and clumsy because of great weight.

• 2 dull or laborious.

– derivatives
ponderosity noun,
ponderously adverb,
ponderousness noun.

– origin ME: via Fr. from L. ponderosus, from pondus, ponder- ‘weight’.