coo

noun2

1. •
   The murmuring sound made by a dove or pigeon.

   • The male [ring dove] will continue nest-coos for 3–4 days until his female partner begins to nest-coo. At that point the male's nest-coo begins to become less frequent[…]. — 1979
2. •
   (figurative) An expression of pleasure made by a person.

verb2

1. •
   To make a soft murmuring sound, similar to a dove or pigeon.

   • No birds, except as birds of passage, flew, / No bee was known to hum, no dove to coo. — 1763
2. •
   To speak in an admiring fashion, to be enthusiastic about.

   • They were too busy cooing over the baby and his parents were too busy cooing over each other. — 2013

exclamation1

1. •
   An expression of approval, surprise, etc.

   • The last track on each of the three sections is a professional course, where you can customise your bike by changing the tyres and the size of chainwheel. Coo! — 1988

noun2

1. •
   Initialism of chief operating officer.
2. •
   Initialism of country of origin.