Open English Wordnet
Nouns
(n)underestimate, underestimation, underrating, underreckoningan estimation that is too low; an estimate that is less than the true or actual value
Verbs
(v)undervalue, underestimateassign too low a value to“Don't underestimate the value of this heirloom-you may sell it at a good price”
(v)lowball, underestimatemake a deliberately low estimate“The construction company wanted the contract badly and lowballed”
(v)underestimate, underratemake 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”