daddy longlegs Meaning, Definition & Usage

  1. noun long-legged slender flies that resemble large mosquitoes but do not bite
    crane fly.
  2. noun spiderlike arachnid with a small rounded body and very long thin legs
    Phalangium opilio; harvestman.

WordNet

Dad"dy long"legs`
Definitions
  1. (Zoöl.) An arachnidan of the genus Phalangium, and allied genera, having a small body and four pairs of long legs; -- called also harvestman, carter, and grandfather longlegs.
  2. (Zoöl.) A name applied to many species of dipterous insects of the genus Tipula, and allied genera, with slender bodies, and very long, slender legs; the crane fly; -- called also father longlegs.

Webster 1913