|on moral grounds
||based on what is right and wrong
||We refuse to accept money from drug dealers - on moral grounds.
|on my back
||criticizing me, on my case, ride me
||The coach is on my back about missing the game last week.
|on my best behavior
||being polite to everyone, behaving in an appropriate manner
||I promised my mother that I will be on my best behavior at
her wedding. I will be a very good boy.
|on my case
||looking for my mistakes, criticizing me
||The coach is on my case again, yelling at me to play harder.
|on my deathbed
||nearly dead, very ill, at death's door
||I was so sick, I thought I was on my deathbed.
|on my good side
||to become my friend, in my good books
||He says nice things to me, hoping to get on my good side.
|on my plate
||on my schedule, on my list of duties or tasks
||I have too much on my plate right now. I'm too busy.
|on my way
||continue my journey, departing
||Before I leave, I'd like a cup of coffee. Then I'll be on my way.
|on my word
||(See upon my word)
|on our last legs
||nearly dead or bankrupt, nearly done for
||Financially, we were on our last legs. We couldn't get a loan.