Alternative form of fool's cap / (strictly) Writing paper sheets measuring 13.25 x 16.5 inches / (more usually) Such a sheet folded or cut in half, thus approximately 8 x 13.25 inches.

(of a device) Protected against, or designed to be proof against, misuse or error. / (of an idea or plan) Certain to succeed in all eventualities, or claimed to be so; infallible.

(transitive) To render foolproof.

Marked by unthinking recklessness with disregard for danger; boldly rash; hotheaded.

A person who is foolhardy.

In a foolish manner. / Without good judgment.

Foolish behaviour or speech.

The quality of being foolhardy.

In a foolhardy manner

(archaic) second-person singular simple present form of fool