1. That cannot be surmounted or overcome.

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

• incermountable,
• insurrmountable,
• insormountable,
• unsermountable,
• insurmoutable,
• insourmountable,
• insurmontable,
• insermountable,
• unsormountable,
• insumountable,
• unsurmountasble,
• unsurmountable,
• jnsurmountable,
• insuremountable,
• insurtmountable,
• insurmountabel,
• insurmountabble,
• insurmountible,
• insurmounteble,
• in surmountable

The adverb form of the word "insurmountable" is "insurmountably".

The adjective form of the word "insurmountable" is "insurmountable". The word functions as an adjective in itself to describe something that cannot be overcome or conquered.

The plural form of "insurmountable" is "insurmountables".

The singular form of the word "insurmountable" is "insurmountable" itself. The word does not change in form between singular and plural usage.