Incapable of flying. Used of certain birds, such as the penguin.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "flightless" in a sentence
"UPDATE: SO, I am told by doctor that I have, in all likelihood, a post-viral infection, brought on and perpetuated by being consistently run aground by the Great Yellow Budgerigar, which, although flightless, is a fast-moving and demanding creature."
"Even the flying spaghetti monster on Futurama: "You seriously believe I'm descended from some kind of flightless manicotti?""
"This neatly solves the age-old problem of how "flightless" birds could have reached the different continents: they were not flightless at all, and simply flew."