1.AdjectiveUnable to fly.
Describing kinds of birds that normally cannot fly, such as the penguin, ostrich, and emu."The indigenous fauna of Australia and New Zealand featured an especially interesting array of flightless birds.; The animal shelter has a flightless sparrow named Shiny, who seems to make up for his disability by being an avid runner.; Oh great, some wind is blowing in Chicago, so now I'm flightless in Seattle, because this airline can't cope!"
4.AdjectiveSuddenly deprived of a scheduled (airline) flight by its cancellation."Oh great, some wind is blowing in Chicago, so now I'm flightless in Seattle, because this airline can't cope!"