Used especially in economics and finance to describe a market, price, or economic indicator reaching its lowest point and beginning to stabilize or recover.
景気は底打ちしたと見られる。
The economy appears to have bottomed out.
株価の底打ち感が出てきた。
There is a sense that stock prices have bottomed out.
Stock prices finally bottomed out.
エコノミストたちは景気の底打ちを確認した。
The economists confirmed that the economy had bottomed out.
天井 refers to a market's peak or highest point, the opposite of the low point described by 底打ち.
底値 is the lowest price itself, while 底打ち describes the event or process of prices reaching that bottom.
Compound of 底 (そこ, 'bottom') and 打ち (うち, the continuative form of 打つ 'to hit'), literally 'hitting the bottom'. The term is a calque from English 'bottom out'.