Aerostatic is a term that refers to an object that is static in the air, such as a balloon. There are several synonyms for aerostatic that can be used depending on the context. One of the closest synonyms is buoyancy, which refers to the upward force exerted on an object by the fluid (in this case, air) in which it is immersed. Other synonyms include levitation, suspension, and floating. These terms are related to objects that are suspended in the air, but each has a slightly different connotation. Overall, there are many words that can be used to describe the concept of an object remaining still in the air, making it important to choose the right word based on the desired meaning.