Appiah often used the words thick and thin to describe words applied to morality. Thin words are words that are universal across many nationalities and cultures, such as "good" and "bad". Thin words describe something, but do not really hold too much depth and meaning. Thick words, however, add much more meaning to a description. These words are more special and specific to certain cultures and their histories and traditions. As examples, Appiah used "courageous" and "rudeness". These apply more to particular social contexts, and you have to think of the act you are describing. Thick words are exactly as they imply, they are thick with meaning and background and thought.