noun
swallowing in one gulp; downing; mouthful; bite
Refers to consuming something in a single swallow or bite. Often used with で or as a counter-like noun.
彼は薬を一飲みで飲み込んだ。
He swallowed the medicine in one gulp.
そのケーキは一飲みで食べられる大きさだった。
The cake was small enough to eat in one bite.
noun
sipping; sip
A small drink, often used when taking a sip of something like tea or alcohol. Less common than sense 1.
熱いお茶を一飲みして、ほっとした。
I took a sip of hot tea and felt relieved.
noun
thinking nothing of one's opponent; making easy prey of someone
Idiomatic use: treating an opponent as if they can be swallowed in one gulp. Often appears in phrases like 一飲みにする.
彼は相手を一飲みにするつもりで試合に臨んだ。
He approached the match intending to make short work of his opponent.
一口 is more common for 'one bite' or 'one mouthful' and is used in broader contexts, while 一飲み emphasizes the act of swallowing or drinking in one go.
Compound of 一 (one) and 飲み (drinking/swallowing, from 飲む). The idiomatic sense likely derives from the metaphor of swallowing an opponent whole.