The antonyms for the phrase "more rib-tickling" can include words such as dull, tedious, and boring. These words suggest a lack of humor, laughter, and excitement. Other antonyms could include serious, somber, and grave, which implies a solemn and sober tone. These words are often used to describe serious topics, such as politics, economics, or social issues. They can also be used to describe environments that do not lend themselves to laughter or humor, such as a library or a funeral. Choosing the right antonym for "more rib-tickling" is a matter of context and the desired tone of the message.