Definitions of underestimate:
- noun: an estimation that is too low; an estimate that is less than the true or actual value
- verb: make too low an estimate of
Example: "He underestimated the work that went into the renovation"
- verb: make a deliberately low estimate
- verb: assign too low a value to
Example: "Don't underestimate the value of this heirlooom-you may sell it at a good price"