An Etymological Dictionary of Astronomy and Astrophysics

1. Not clearly or explicitly stated or expressed.
   

2. Indefinite or indistinct in nature or character, as ideas or feelings.
   

3. Not definitely established, determined, confirmed, or known; uncertain (Dictionary.com).

→ ambiguous, → nebulous, → indefinite, → fuzzy, → unclear.

Etymology (EN): M.E., from M.Fr. vague “empty, vacant; wild, uncultivated; wandering,” from L. vagus “wandering, rambling,” of unknown origin.

Etymology (PE): Gereng, from Kalidari gereng “wandering,” Kurd. (Kurmanji) garin, (Sorani) garân “to wander,” Dehxodâ gereng “shattered;” ultimately from Proto-Ir. *gar-an-ka-, from *gar- “to turn, to wind” (Cheung 2007).