underestimate

(noun) an estimation that is too low; an estimate that is less than the true or actual value. Synonyms: underestimation, underrating, underreckoning.

(verb) assign too low a value to. Synonyms: undervalue. Example: "Don't underestimate the value of this heirloom-you may sell it at a good price."

(verb) make a deliberately low estimate. Synonyms: lowball. Example: "The construction company wanted the contract badly and lowballed."

(verb) make too low an estimate of. Synonyms: underrate. Examples: "He underestimated the work that went into the renovation." "Don't underestimate the danger of such a raft trip on this river."