splash the boots

to urinate

Verb, transitive: "To splash my boots" is a British army expression meaning to go for a pee in the outdoors (on manoueuvres, etc. when a regular lavatory isn't available.) The action of forceful micturation against a tree or similar tends to cause a splashback onto the boots.

In Australia the act of urinating, male...although some women have been known to uniate while standing.