GNU Collaborative International Dictionary of English

Found one definition

1.       
   Croon, v. t. [imp. & p. p. Crooned (kro͞ond); p. pr. & vb. n. Crooning.]
   1. To sing in a low tone, as if to one's self; to hum.
   
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   Hearing such stanzas crooned in her praise. C. Bronté.
   
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   2. To soothe by singing softly.
   
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   The fragment of the childish hymn with which he sung and crooned himself asleep. Dickens.
   
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