noun
Refers to the projecting part of a container (teapot, kettle, watering can, etc.) from which liquid is poured.
急須の注ぎ口からお茶を注ぐ。
Pour tea from the spout of the teapot.
やかんの注ぎ口が欠けてしまった。
The spout of the kettle got chipped.
Irregular okurigana usage; less common.
注ぎ口 specifically means a spout or pouring opening, while 口 is a general word for mouth, opening, or entrance.
Compound of 注ぎ (tsugi, the continuative form of 注ぐ 'to pour') + 口 (kuchi 'mouth, opening').