The Collaborative International Dictionary
Disallowable
Disallowable \Dis`al*low"a*ble\, a.
Not allowable; not to be suffered.
--Raleigh. --
Dis`al*low"a*ble*ness, n.
Douglas Harper's Etymology Dictionary
disallowable
mid-15c., from disallow + -able.
Wiktionary
disallowable
1 able to be disallow#Ver
2 Not allowable; not to be suffered or permitted; which should not be allowed.