a haunting creature of the ruined wilderness, most likely a restless desert spirit invoked alongside real night animals in a picture of total desolation
This word appears only once in the whole Bible, in Isaiah's vision of Edom reduced to a wasteland (Isaiah 34:14). It sits in a list of creatures that will take over the ruins: wild animals, howling beasts, a wild goat calling to its mate, and this figure, which then settles down and finds itself a resting place. Because the word is used just once, and because Isaiah is deliberately painting a scene of dread, its exact identity has been argued over for centuries.
The two poles of the debate are whether it names an ordinary night bird (something like a screech owl or nightjar, fitting the birds nesting and brooding in the very next verse) or a female desert spirit borrowed from the older cultures of Mesopotamia, where a class of restless spirits was thought to haunt lonely places. Most standard reference works, and every ancient translation of Isaiah, lean toward the spirit reading. That does not mean the fully developed figure that later Jewish folklore called Lilith (Adam's rebellious first wife, a stealer of babies) is present here. That character grew up much later. In Isaiah the word most likely points to a nameless haunting creature of the ruined land, one of many signs that Edom has been handed over to chaos and emptiness.
The famous name Lilith comes from this single verse, but the personality attached to it does not. Reading the later legend back into Isaiah is the main trap this word sets.