The phrase "bills and coo" commonly refers to affectionate behavior between two people. However, there are multiple antonyms for this phrase, which describe negative or non-affectionate behavior. For instance, "cold shoulder" refers to ignoring or showing indifference towards someone. "Harsh words" refer to using critical or unsympathetic language. "Frosty reception" refers to being unwelcoming, distant or aloof. "No love lost" indicates there is no affection or warmth between two people. "Bitter arguments" refer to fights or intense disagreements. Overall, these words are used to describe situations where couples are not showing love or fondness towards each other.