A gate machine at train station entrances/exits that reads tickets or IC cards and automatically controls passage.
改札機にSuicaをタッチしてホームに入った。
I tapped my Suica on the ticket gate and entered the platform.
朝のラッシュで改札機の前に列ができていた。
There was a line in front of the ticket gates during the morning rush.
改札機が故障して通れなかったので駅員に声をかけた。
The ticket gate malfunctioned and I couldn't pass, so I called a station attendant.