expression, noun-modifying (irregular)
Describes behavior, ideas, or actions that deviate from normal standards or common sense. Often used in formal or critical contexts.
彼の常軌を逸した行動に、周囲は困惑した。
People around him were baffled by his aberrant behavior.
その計画は常軌を逸していると批判された。
The plan was criticized as being out of line with common sense.
異常 is a general adjective/noun for 'abnormal', whereas 常軌を逸した is a stronger, more literary expression specifically for behavior or ideas that are wildly off track.
A set phrase combining 常軌 (normal course/track) with 逸する (to deviate). The literal meaning is 'deviated from the normal track', used figuratively for aberrant behavior.