This is the 8266th most frequent Polish word.
pisu
"Pisu" does not have a standalone meaning in Polish; it may be a misspelling or part of a phrase.
Here, 'Pisu' refers to a proper noun, possibly a place name.
W weekend pojedziemy na piknik do lasku niedaleko Pisu.
On the weekend, we will go for a picnic in the grove near Pisu.
Here, 'Pisa' is the name of a river, demonstrating the locative case in Polish.
Podczas wędrówki nad Pisą zgubiliśmy mapę.
While hiking near Pisa, we lost our map.
In this sentence, 'PiS' refers to a political entity, specifically 'Prawo i Sprawiedliwość,' a Polish political party.