noun
winning lottery ticket; prize-winning ticket
Refers specifically to a lottery or raffle ticket that has won a prize. Not used for general winning tickets (e.g., sports events).
宝くじの落ち札を確認したら、1万円当たっていた。
When I checked the winning lottery ticket, I had won 10,000 yen.
落ち札の番号が発表された。
The winning ticket numbers have been announced.
当たりくじ is a more general term for a winning ticket in any kind of drawing or lottery, while 落ち札 specifically emphasizes the ticket itself as the prize-winning one.
落札 (らくさつ) means 'successful bid' in an auction, a completely different word despite sharing the same kanji form as one spelling of 落ち札.
Compound of 落ち (ochi, 'falling', from verb 落ちる) and 札 (fuda, 'ticket, tag'). The 'falling' likely refers to the idea of a prize 'falling' to the winner, similar to the English expression 'the lot fell on'.