See more synonyms for blue-sky on
  1. fanciful; impractical: blue-sky ideas.
  2. (especially of securities) having dubious value; not financially sound: a blue-sky stock.

Origin of blue-sky

First recorded in 1890–95 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for blue sky



  1. (modifier) of or denoting theoretical research without regard to any future application of its resulta blue-sky project
verb -skies, -skying or -skied
  1. to theorize (about something that may not lead to any practical application)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012