1. Not capable of being defined; unsusceptible of definition.

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

• undefendable,
• undeinable,
• undenable,
• indifinable,
• undefineable,
• undeinably,
• undenieable,
• undefensable,
• indefinible,
• undinable,
• undefeneable,
• 7ndefinable,
• undefinble,
• endefinable,
• undeninable,
• undefanable,
• undefinible,
• undefinanced,
• undepozable,
• unxaminable

• unadoptable,
• undefendable,
• uneatable,
• undependable,
• undefeated,
• undefiled,
• unadaptable,
• undefined,
• unadvisable,
• undependably.

The adjective form of "undefinable" is "undefined".

The plural form of "undefinable" is "undefinables".

The singular form of the word "undefinable" is "undefinable". In English, the word does not change when referring to singular or plural subjects.