for a moment—very briefly; for a short time:
- He might have popped in for a moment, since he was passing this way.
Note: The expression is not antonymous in meaning to the phrase not for a moment—(emphatic) absolutely never (also: not for one moment):
- Not for a moment would I suggest that you did it deliberately.
for the moment—at present; for the time being:
- Sorry, Mr. Rathbone, I’m tied up for the moment, but I can see you later today.