1. underestimate, underestimation, underrating, underreckoning, estimate, estimation, approximation, idea
usage: an estimation that is too low; an estimate that is less than the true or actual value
Verb
1. underestimate, underrate, misjudge
usage: make too low an estimate of; "he underestimated the work that went into the renovation"; "Don't underestimate the danger of such a raft trip on this river"