daddy longlegs

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various arachnids of the order Opiliones, having a small rounded body and long slender legs.
• noun Chiefly British A crane fly.

from The Century Dictionary.

• noun In Great Britain, a name of tipularian dipterous insects, or crane-flies, of the family Tipulidæ. Also called father-long-legs and Harry-long-legs.
• noun In America, a popular name of the opilionine or phalangidean arachnids or harvestmen, spider-like creatures with small rounded bodies and extremely long, slender legs. Also called grandfather-long-legs and granddaddy-long-legs. See Phalangium.

from the GNU version of the Collaborative International Dictionary of English.

• (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.
• (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun UK, Ireland The cranefly; any insect of the family Tipulidae.
• noun Australia, Canada, New Zealand, US Any (non-spider) arachnid of the order Opiliones, mostly with long thin legs; the harvestman.
• noun loosely The daddy long-legs spider, any spider of the family Pholcidae.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun long-legged slender flies that resemble large mosquitoes but do not bite
• noun spiderlike arachnid with a small rounded body and very long thin legs