'Coo' definitions:

Definition of 'coo'

From: WordNet
noun
The sound made by a pigeon
verb
Speak softly or lovingly; "The mother who held her baby was cooing softly"
verb
Cry softly, as of pigeons

Definition of 'Coo'

From: GCIDE
  • Coo \Coo\, v. i. [imp. & p. p. Cooed; p. pr. & vb. n. Cooing.]
  • 1. To make a low repeated cry or sound, like the characteristic note of pigeons or doves. [1913 Webster]
  • The stockdove only through the forest cooes, Mournfully hoarse. --Thomson. [1913 Webster]
  • 2. To show affection; to act in a loving way. See under Bill, v. i. "Billing or cooing." --Byron. [1913 Webster] Cooey