noun
coin return slot; change slot
Refers to the slot on a vending machine, ticket machine, or similar device where coins are returned as change.
自動販売機の釣り銭口からお釣りを取り忘れないでください。
Please don't forget to take your change from the vending machine's coin return slot.
釣り銭口に手を入れて、残った硬貨を探した。
I put my hand into the change slot and felt around for leftover coins.
Compound of 釣り (つり, 'change' from 釣る 'to fish/make change') + 銭 (せん, 'coin') + 口 (ぐち, 'mouth/opening'). The reading せん for 銭 is a relatively common Sino-Japanese reading in compounds.