1. N-SING Theonsetof something is the beginning of it, used especially to refer to something unpleasant. (尤指不愉快事情的) 開始

Most of the passes have been closed with the onset of winter. 隨著冬天的來(lái)臨，大多數(shù)的關(guān)卡都已經(jīng)關(guān)閉。