The shower, especially a standalone shower that is not part of a bathtub. There isn't a proper bathroom in the studio apartment, just a toilet and a tiny rain closet. Let me just get in the rain closet to wash all this dirt and grime off before dinner.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
n. a shower (bath). P.U. Willy. You need a trip to the rain closet.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.