As a verb unfill
is (obsolete) to empty.
As an adjective unfillable is
not fillable; not able to be filled.
unfill
English
Verb
(
en verb)
(obsolete) To empty
*1606 - , act ii, scene 2
*:I'll pierce him to his face; he shall die looking upon me. Thy veins are swell'd with lust; this shall unfill 'em
unfillable
English
Adjective
(-)
Not fillable; not able to be filled.
Able to be unfilled.