noun
brief door opening; momentary door opening
Rare term used in railway contexts for briefly opening a door, e.g., when a passenger's foot is caught. Not in general use.
駅員が小開扉を行い、挟まった靴を引き抜いた。
The station staff performed a brief door opening and pulled out the stuck shoe.
Compound of 小 (small, brief) + 開扉 (opening a door). The exact origin is uncertain; likely a technical coinage in railway operations.