flightless

"Flightless" usually describes birds that cannot fly. Think of an ostrich racing across open land, a penguin cutting through icy water, or a kiwi moving quietly through the forest at night. Instead of flying, these animals survive in other ways, often with strong legs, solid bodies, or great skill in the water.

The word is most often used for animals, especially birds that evolved over time without the power of flight. In many cases, this is not a weakness at all. Penguins do not need to fly because they are built for swimming, and ostriches are built for speed on land.

The word "flightless" most often refers to birds that cannot fly. Some birds lost this ability over a long time through evolution, especially in places where flying was less important for survival. Ostriches, emus, kiwis, cassowaries, and penguins are well-known examples. A few insects can also be described this way if they have no working wings or cannot use them for flight, but birds are by far the most common context.

This does not simply mean weak or limited. Many flightless birds are highly suited to the places where they live. Ostriches have powerful legs and can run very fast. Penguins are excellent swimmers, and their bodies are shaped for moving through water rather than air. In this way, the word often suggests a different kind of strength: not life in the sky, but life adapted to the ground, the forest, or the sea.

The word can sometimes be used in a figurative way for something that never quite rises, advances, or takes off, but that use is much less common. In ordinary English, "flightless" mainly brings to mind animals, especially birds, that live fully without flying.