noun

• (by extension) An expression of pleasure made by a person.
  "An infant has only cries and coos with which to communicate distress and well-being. Adults have many more ways of expressing themselves. However, their expressions of disease and ease can be boiled down to sophisticated cries and coos. A call for help in whatever form is a cry. A sense of well-being however expressed is a coo. Healing in the context of cries and coos can be viewed as the process of resolving the cries and fostering the coos."

verb

• (ambitransitive) To make a soft murmuring sound, as a pigeon.
  "No birds, except as birds of paſſage, flew, / No bee was known to hum, no dove to coo."
• (intransitive) 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."

adj

• (slang) Cool.

noun

• (international trade) Initialism of country of origin.