first: you give me a wrong pronunciation,you should say 甩 (shuai 3),not 甩 (shuia3) second: when you saw the word of 甩 to write on the window of stores/shops , it means they sell some goods at a pretty low price , it is a sales promotion. i hope the answer can help you understand!

First, “甩卖”，it should be a phrase. 甩 is like throwing away or giving up stuff. it means sth is very very cheap, sth is on sale.

it is not formal chinese,just ignore it,just likes亏本大甩卖、跳楼价。

General in buying and selling is used to reduce the prices of exaggeration claim.

maybe means something is on sale