"Bills and coos" is a phrase used to describe the affectionate or lovey-dovey talk between two people in a romantic relationship. As with many phrases, there are other ways to describe this type of interaction. Some synonyms for "bills and coos" might include "sweet talk," "flirting," "cooing," or "love talk." "Whispering sweet nothings" is another common phrase for this type of behavior. In general, these terms all refer to the gentle and intimate conversations that happen between two people who are falling in love or maintaining a romantic relationship. These words can be used to add color and nuance to descriptions of romantic interactions in literature or other artistic works.