• unflimable,
• unfilmabel,
• unfilamble,
• unfilmible,
• unvilmable

• unbridgeable,
• unreachable,
• unthinkable,
• unflappable,
• unchangeable,
• unforeseeable,
• unfathomable,
• unbreakable,
• unstoppable,
• unshakeable.

The adjective form of "unfilmable" is "unfilmable" itself. It does not change in form when used as an adjective.

The plural form of the word "unfilmable" is "unfilmables".

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