Available Definitions:
1) v. i. - To make a continuous hollow moan, as cattle do when in pain.
2) v. i. - To hum or sing in a low tone; to murmur softly.
3) v. t. - To sing in a low tone, as if to one's self; to hum.
4) v. t. - To soothe by singing softly.
5) n. - A low, continued moan; a murmur.
6) n. - A low singing; a plain, artless melody.