Simple past tense and past participle of ad-lib.(verb)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "ad-libbed" in a sentence
"Connery "wanted me to do it first, in case I ad-libbed anything that wasn't in the script he could respond.""
"In previous projects, he's directed his actors to improvise for hours, sometimes sending them onto London streets in character, then drawing out a story from this trove of ad-libbed material."
"Mr. Doremus says that much of the film, which was made for less than $500,000, was ad-libbed, based on a 50-page outline that contained subtext, plot points and objectives for each scene."