quick and energetic; "a brisk walk in the park"; "a lively gait"; "a merry chase"; "traveling at a rattling rate"; "a snappy pace"; "a spanking breeze"
an estimation that is too low; an estimate that is less than the true or actual value
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"