The phrase "jest at" is a relatively specific expression, meaning to mock or make fun of someone in a lighthearted way. Some synonyms for "jest at" include "tease," "ridicule," "banter with," "poke fun," and "rib." However, it's important to note that not all of these synonyms have the same connotation as "jest at," which typically implies a friendly or playful tone. Some of these alternative terms may be more aggressive or insulting, so it's important to choose the right word for the context of your sentence. Other possible synonyms for "jest at" could include "joke around with," "playfully tease," or "mock in a good-natured way".