There are various synonyms that can be used for the phrase "make less sensitive". One such word is desensitize, which refers to the process of making something or someone less sensitive to a particular stimulus. Another synonym is numb, which means to reduce the ability to feel a sensation. Dull and deaden are other synonyms that can be used for the same purpose. Diminish, reduce, and lessen are some of the other words that can be used to convey the idea of decreasing sensitivity. Overall, there are many words that can be used to describe the process of making something or someone less sensitive, depending on the context and the specific connotations that one wants to convey.