Source : Webster's Revised Unabridged Dictionary (1913)

Solidly \Sol"id*ly\, adv.
   In a solid manner; densely; compactly; firmly; truly.

Source : WordNet®

solidly
     adv 1: as an undiversified whole; "the unions voted solidly for
            Roosevelt"
     2: with strength and soundness; "a solidly built house"