There are several synonyms for the phrase "makes up as one goes along" which means to improvise or come up with something on the spot without prior planning or preparation. One such synonym is "winging it," which conveys a sense of spontaneity and flying by the seat of one's pants. Another synonym is "ad-libbing," which refers to improvising while performing or speaking. "Spontaneous" and "unrehearsed" are also good synonyms that describe the same idea. Ultimately, all of these synonyms suggest a certain level of creativity and resourcefulness that can be useful in many different situations, from impromptu speeches to unexpected challenges in daily life.