资料来源 : Webster's Revised Unabridged Dictionary (1913)

Croon \Croon\, v. t. [imp. & p. p. {Crooned} (kr??nd); p. pr. &
   vb. n. {Crooning}.]
   1. To sing in a low tone, as if to one's self; to hum.

            Hearing such stanzas crooned in her praise. --C.
                                                  Bront?.

   2. To soothe by singing softly.

            The fragment of the childish hymn with which he sung
            and crooned himself asleep.           --Dickens.

资料来源 : WordNet®

crooning
     n 1: singing in a soft low tone; "her crooning soon put the child
          to sleep"
     2: the act of singing popular songs in a sentimental manner