noun which may take the genitive case particle 'no', na-adjective, noun
unconventional; eccentric; out of touch with common sense
Describes a person, behavior, or idea that deviates from what is generally considered sensible or normal. Often carries a negative or critical tone.
彼の常識はずれな発言に、みんな驚いた。
Everyone was surprised by his unconventional remark.
そんな常識はずれの計画は通らないよ。
Such an outlandish plan won't be accepted.
非常識 is a more direct and common word for 'lacking common sense' or 'thoughtless', while 常識はずれ emphasizes deviation from norms, often with a nuance of eccentricity.
Compound of 常識 (common sense) and はずれ (外れ, 'off, outside'). Literally 'off from common sense'.