A bird nest is a place where a bird lays its eggs. There are all kinds of nests, including cup nests, holes in the ground, and piles of twigs and leaves. The word can be used as a noun or a verb, as in – a bird nests in a nest. They are in all kinds of sizes: some can be as big and heavy as a car, like an old eagle's nest, while some can be tiny as a thimble, like the nest of a bee hummingbird.