Cointreau is a premium triple sec liqueur made from the essence of sweet oranges. There are a few synonyms that can be used to describe Cointreau. Firstly, it could be referred to as an orange liqueur, given its primary flavor profile. Secondly, it could be described as a curaçao, which is a type of liqueur similar in taste and aroma to Cointreau, but often made with a blend of bitter and sweet oranges. Another synonym could be Grand Marnier, another high-end orange-flavored liqueur. Lastly, Cointreau could also be called a high-end spirit or a luxury liquor because of its premium quality and reputation.