Standing up:站立着：The crowd was on its feet for the last ten seconds.人群都站立着渡过了最后的十秒钟
Fully recovered, as after an illness or convalescence:康复：疾病或渐愈之后完全康复：The patient is on her feet again.病人复原了
In a sound or stable operating condition:非常稳定，正常的运转状态：put the business back on its feet after years of mismanagement.这几年管理失误，现在该让业务正常运转起来了
In an impromptu situation; extemporaneously:即席的；无准备的："Politicians provide easy targets for grammatical nitpickers because they have to think on their feet"(Springfield MA Morning Union)“政客们很容易被挑剔语法的人树为靶子，因为他们必须即席思考”(斯普林菲尔德MA早晨联合报)