1. That may not be allowed.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• ynallowable,
• hnallowable,
• jnallowable,
• inallowable,
• 8nallowable,
• 7nallowable,
• uballowable,
• umallowable,
• ujallowable,
• uhallowable,
• unzllowable,
• unsllowable,
• unwllowable,
• unqllowable,
• unaklowable,
• unaplowable,
• unaolowable,
• unalkowable,
• unalpowable,
• unaloowable

• unalterable,
• unadaptable,
• unacceptable,
• unattainable,
• unaffordable,
• unwearable,
• Unallowances,
• Unallowing,
• unavailable,
• Unallowanced.

The adjective form of "unallowable" is "unallowable".

The plural form of the word "unallowable" is "unallowables".

The singular form of the word "unallowable" is "unallowable".