(a) ayakta durmak/kalmak, yürümek, taban tepmek.
I'm on my feet all day long. (b) iyileşmek, (hastalıktan) iyileşip ayağa kalkmak.
This medicine will soon have you on your feet again. (c) (konuşmak üzere) ayağa kalkmak.
No sooner had the question been put than he was on his feet to reply.