Ad lib and Off the top of one's head

Ad lib adverb - Without advance preparation.

Off the top of one's head and ad lib are semantically related. in off the cuff topic. In some cases you can use "Off the top of one's head" instead an adverb phrase "Ad lib". informal substitute

Ad lib and off the top of one's head are semantically related. Sometimes you can replace phrase "Ad lib" with "Off the top of one's head", this phrases are similar.