If you murmur something, you say it very quietly, so that not many people can hear what you are saying.

A murmur is something that is said which can hardly be heard.

A murmur is a continuous low sound, like the noise of a river or of voices far away.

A murmur of a particular emotion is a quiet expression of it.

A murmur is an abnormal sound which is made by the heart and which shows that there is probably something wrong with it.

If someone does something without a murmur, they do it without complaining.