also: ぴんさつ
noun
crisp new banknote
Colloquial term for a brand-new, unwrinkled bill, often used when giving money as a gift or for special occasions.
お年玉はピン札で用意した。
I prepared the New Year's gift money in crisp new bills.
銀行でピン札に両替してもらった。
I had the money exchanged for crisp new bills at the bank.
新札 is the standard word for a new banknote, while ピン札 is a colloquial term emphasizing the crisp, unwrinkled condition.
The ピン part likely comes from the onomatopoeic or mimetic word ピン, suggesting something taut or crisp, combined with 札 (bill). The exact derivation is uncertain.