a. 不能分解的, 不能分离的, 不能解决的

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.
[1913 Webster +PJC]