The Collaborative International Dictionary
Irresolvable nebulae
Irresolvable \Ir`re*solv"a*ble\, a. [Pref. ir- not + resolvable. Cf. Irresoluble.] Incapable of being resolved; not separable into component parts.
Irresolvable nebul[ae] (Astron.), nebul[ae] of a cloudlike
appearance, which have not yet been resolved by the
telescope into stars, and are often distant galaxies. See
galaxy[2].
--Sir W. Herschel.