noun
disposal sale; surplus goods sale
A sale event where excess, discontinued, or unwanted items are sold off, often at reduced prices. The term is not extremely common but is understood in commercial contexts.
デパートで処分市をやっている。
They're having a disposal sale at the department store.
処分市で安く買った家具だ。
This is furniture I bought cheaply at a surplus sale.
Means 'inventory clearance'; 処分市 is the actual sale event, while 在庫一掃 describes the purpose.
Compound of 処分 (disposal) and 市 (market/sale). The exact historical derivation is uncertain, but it follows a common pattern for naming commercial events.