adj. 1 cloudlike. 2 a formless, clouded. b hazy, indistinct, vague (put forward a few nebulous ideas). 3 Astron. of or like a nebula or nebulae. nebulous star a small cluster of indistinct stars, or a star in a luminous haze. nebulosity n. nebulously adv. nebulousness n.
[ ME f. F nébuleux or L nebulosus (as NEBULA) ]