(1):

(n.) A low, continued moan; a murmur.

(2):

(v. t.) To soothe by singing softly.

(3):

(n.) A low singing; a plain, artless melody.

(4):

(v. t.) To sing in a low tone, as if to one's self; to hum.

(5):

(v. i.) To hum or sing in a low tone; to murmur softly.

(6):

(v. i.) To make a continuous hollow moan, as cattle do when in pain.