Faucet
Tap
noun
This isn't a literal snake's mouth, but rather a faucet. They do kind of have a resemblance though, just think about how the shape of a faucet kind of resembles that of a snake, with water coming out of its mouth.
This one's a little unique, as it uses on'yomi for 蛇, and kun'yomi (which gets rendaku'd) for 口. You didn't learn this reading for 蛇, so here's a mnemonic to help you:
Every time you try to drink from the faucet, you get viciously attacked by a jaguar (じゃ). Trying to drink from the faucet has become a fight for life and death. You just know the jaguar is hiding right there behind the faucet, guarding it.
蛇口をひねる
to twist the faucet
蛇口を閉める
to shut off the faucet
蛇口を開ける
to open the faucet
蛇口を回す
to turn the faucet
ホースの蛇口
faucet of a hose
水道の蛇口
tap water faucet
台所の蛇口
kitchen faucet
蛇口から出る
to come out from the faucet
蛇口から飲む
to drink from the faucet
蛇口から流れ出る
to flow out from the faucet
蛇口がちゃんと閉まってなかったよ！
The faucet wasn't properly closed!
ホースの蛇口が壊れて水が止まらなくなってるんだ。
The faucet of the hose is broken, and the water won't stop.
ちょっと、蛇口から直接飲むのはやめてって言ってるじゃん！
Hey, I've been telling you to stop drinking directly from the tap!