The phrase "bob about" refers to a movement that is characterized by quick and sudden up and down motions. There are several synonyms you can use to describe this movement, including "bounce," "jiggle," "wobble," "flounder," "toss," and "pitch." Another popular synonym for "bob about" is "bobble," which is frequently used to denote a repeated and irregular motion that is often accompanied by a rattling or shaking sound. Whether you're trying to describe the movement of a bouncing ball, a person on a bumpy ride, or a boat in choppy waters, these synonyms for "bob about" can help you paint a vivid picture for your readers or listeners.