1. Standing up: The crowd was on its feet for the last ten seconds.
2. Fully recovered, as after an illness or convalescence: The patient is on her feet again.
3. In a sound or stable operating condition: put the business back on its feet after years of mismanagement.
4. In an impromptu situation; extemporaneously: "Politicians provide easy targets for grammatical nitpickers because they have to think on their feet"(Springfield MA Morning Union).