nebulous

Etymology

From Middle English, from Middle French nebuleus, from Latin nebulōsus (“full of mist, foggy, cloudy”), from nebula (“mist, vapour, cloud”), from Proto-Indo-European *nébʰos (“cloud, vapor, fog, moist, sky”). Cognate with Ancient Greek νέφος (néphos, “cloud”), Old High German nebul (“cloud, fog”) (German Nebel), Old English nifol, neowol (“dark, gloomy, obscure, precipitous, prone”). More at neveling, nuel.

adj

1. In the form of a cloud or haze; hazy.
2. Vague or ill-defined.
   The magistrate could not possibly, on the evidence, have held them for a higher court. On the one hand the compositors and pressmen were forced to admit that the light was uncertain, that they were themselves much perturbed, and that it was difficult for them to swear to the identity of the assailants; although they believed that the accused were among them. Cross examined by the clever attorney who had been engaged by McGinty, they were even more nebulous in their evidence. 1915, Arthur Conan Doyle, The Valley of Fear
3. Relating to a nebula or nebulae.