Source : Webster's Revised Unabridged Dictionary (1913)

Immensely \Im*mense"ly\, adv.
   In immense manner or degree.

Source : WordNet®

immensely
     adv : to an exceedingly great extent or degree; "He had vastly
           overestimated his resources"; "was immensely more
           important to the project as a scientist than as an
           administrator" [syn: {vastly}]