"Improvise" means to act or perform spontaneously, without prior preparation or planning. Therefore, the word "improvisationally" can be replaced with a number of synonyms that convey similar meanings. These include words like "spontaneously," "impromptu," "off the cuff," "unrehearsed," and "ad-libbed." Other synonyms that can be used in place of "improvisationally" are "extemporaneously," "unscripted," "on the fly," "unplanned," and "make-shift." No matter which synonym you choose, they will all demonstrate an ability to create something without formal planning or preparation, showing creativity and quick thinking.