piss on v.
1. [17C+] (also piss all over, piss up, piss upon) to treat contemptuously
2. [1950s+] to be drenched with rain.
[1930s+] to hell with; thus excl. piss on it! who cares!
[mid-16C–mid-18C] to be annoyed, uneasy, tetchy; thus on nettles, anxious, uneasy.
[1980s] to blunder, to fail in a task.
[1980s] (Can.) to spoil someone’s plans.
[2000s] to make one’s presence felt, to ‘send a message’.
[1970s+] (orig. US) to shatter illusions, to ruin an otherwise satisfactory situation.
[1970s] (US) to humiliate.
[1950s+] a general insult.