Green’s Dictionary of Slang

piss on v.

[fig. use of piss v. (1)]

1. [17C+] (also piss all over, piss up, piss upon) to treat contemptuously

2. [1950s+] to be drenched with rain.

In phrases

piss on...

[1930s+] to hell with; thus excl. piss on it! who cares!

piss on a nettle (v.)

[mid-16C–mid-18C] to be annoyed, uneasy, tetchy; thus on nettles, anxious, uneasy.

piss on one’s shoe (v.)

[1980s] to blunder, to fail in a task.

piss on someone’s chips (v.)

[1980s] (Can.) to spoil someone’s plans.

piss on someone’s lamp-post (v.)

[2000s] to make one’s presence felt, to ‘send a message’.

piss on someone’s parade (v.) (also piss on someone’s fireworks, rain on someone’s parade, shit on...) [fig. use of SE rain/shit v.]

[1970s+] (orig. US) to shatter illusions, to ruin an otherwise satisfactory situation.

piss on someone’s shoe (v.)

[1970s] (US) to humiliate.

In exclamations

piss on you!

[1950s+] a general insult.