Underestimate
/ʌndɚˈɛs.tɨ.meɪt/
noun
An estimate that is too low.
Synonyms: underestimation
verb
To perceive (someone or something) as having a lower value, quantity, worth, etc., than what he/she/it actually has.
Synonyms: belittle, make light of, misjudge, misunderestimate