neb ‧ u ‧ lous /ˈnebjələs, ˈnebjʊləs/ BrE AmE adjective formal
1 . an idea that is nebulous is not at all clear or exact SYN vague :
‘Normality’ is a rather nebulous concept.
2 . a shape that is nebulous is unclear and has no definite edges:
a nebulous ghostly figure