Definify.com
Webster 1913 Edition
Daddy longlegs
Dad′dy long′legsˊ
.1. 
(Zool.) 
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. 
(Zool.) 
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
.