polysemicadjective.
Describes a word that has multiple meanings.
Example Citation:
"The polysemic champion must be 'set'. Superficially it seems like a wholly unseeming monosyllable, the verbal equivalent of a single-celled organism. Yet it has 58 uses as a noun, 126 as a verb, and 10 as an adjective [and] it take the OED 60,000 words...to discuss them all." —Bill Bryson
Notes:
My vote for the polysemic runner-up would be the word 'round'. It has over 150 separate meanings that consume nearly 8 pages in the OED (and that's not counting 'round' constructions such as 'roundabout', 'rounder', and 'roundhead').
