资料来源 : Webster's Revised Unabridged Dictionary (1913)

Underspend \Un`der*spend"\, v. t.
   To spend less than.

资料来源 : WordNet®

underspend
     v 1: spend less than the whole of (a budget, for example) [ant: {overspend}]
     2: spend at less than the normal rate [ant: {overspend}]