1
finishing in one go;completing in one sitting;(doing something) in a single breath
oft. adverbially as ～に
彼、一気呵成に書き上げたと言ってたけど、この提案書、少し雑だね。
He said he dashed this proposal off in one sitting. It's pretty sloppy.
Other forms
一気かせい 【いっきかせい】 (search-only kanji form)