on the bubble
US informal not certain to get a place in a team, keep your job, win an election, etc.:
Those who had not gained their paramedic certification were " on the bubble" with regard to keeping their jobs.
英语词典包含110679条英英释义在线翻译词条，基本涵盖了全部常用单词的英英翻译及用法，是英语学习的有利工具。