This page provides all possible meanings and translations of the word off-key
false, off-key, sour(adj)
inaccurate in pitch
"a false (or sour) note"; "her singing was off key"
pitched inaccurately either above or below the correct note
not harmonious, or out of accord
Off-key is musical content that is not at the expected frequency or pitch period, either with respect to some absolute reference frequency, or in a ratiometric sense, or pitch intervals not well-defined in the ratio of small whole numbers.
The term may also refer to a person or situation being out of step with what is considered normal or appropriate.