"underrating" in the noun sense
1. underestimate, underestimation, underrating, underreckoning
an estimation that is too low an estimate that is less than the true or actual value
"underrating" in the verb sense
1. underestimate, underrate
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"
Source: WordNet® (An amazing lexical database of English)
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