The term "o-face" is a slang term that refers to the facial expression a person makes during sexual pleasure or orgasm. It is often used in a humorous or teasing context. However, there are many other ways to describe this expression. Some synonyms for the "o-face" include the "pleasure face," the "blissful expression," the "ecstasy face," and the "climax face." Other slang terms that can be used include the "Ooh face" or the "Yes face." Regardless of the term used, the "o-face" is a universally recognized symbol of sexual pleasure and satisfaction.