a hole in a bath, sink, etc. where the water flows away and into which a plug fits （水池、浴缸等的）排水孔，漏眼，渗水孔 
Idioms
(go) down the plughole (British English)
(also (go) down the drain British and North American English)
- (informal)
(to be) wasted; (to get) very much worse （被）浪费掉；（变得）非常糟糕 It's just money down the plughole, you know. 你知道，那只是入不敷出的钱。 Safety standards have gone down the plughole. 安全标准已经过时了。