noun, noun which may take the genitive case particle 'no'
Refers to a situation or outcome that falls short of expectations; often used when hopes or predictions are not met.
試験の結果は当て外れだった。
The exam results were a disappointment.
当て外れな天気でピクニックは中止になった。
The picnic was canceled due to the unexpectedly disappointing weather.
Compound of 当て (ate, 'aim, expectation') and 外れ (hazure, 'miss, failure'). The exact historical derivation is uncertain, but the word literally means 'missing the mark' in terms of expectations.