once again/once more

once again

1. One more time; again. He went over the plan once again, stressing the importance of getting the details exactly right.
2. A phrase used when something is being repeated. Once again, everyone, this paper is due Thursday, not Friday.
3. As has come to be expected. The company has once again proven that they know exactly what consumers want in a premium handheld device.
See also: again, once

once more

1. One more time; again. He went over the plan once more, stressing the importance of getting the details exactly right. I read the instructions once more, just in case there was anything I might have missed. You're getting very good at playing that song, Samantha. Once more, please.
2. A phrase used when something is being repeated. Once more, everyone: this paper is due on Thursday, not Friday, as you were originally told.
See also: more, once
Farlex Dictionary of Idioms.

once more

 and one more time
Please do it one more time. Mary: You sang that line beautifully, Fred. Now, once more. Fred: I'm really tired of all this rehearsing. John (finishing practicing his speech): How was that? Sue: Good! One more time, though. John: I'm getting bored with it.
See also: more, once
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

once aˈgain/once ˈmore

one more time; another time: Once again the train was late. Let me hear it just once more.
See also: again, more, once
Farlex Partner Idioms Dictionary

once more

/again
1. Another time; again: Could you repeat yourself once more?
2. As usual; in typical fashion: Once more, you've proven yourself inept at chess.
See also: more, once
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • once again
  • once and again
  • we must do this again (sometime)
  • back on (one's) feet
  • back on feet
  • Let's do this again
  • let's do this again (sometime)
  • over and over
  • over and over (again)
  • time after time