Ad hoc and Ad lib

Ad hoc adjective - Made or done without previous thought or preparation.

Ad lib and ad hoc are semantically related In some cases you can use "Ad lib" instead an adjective phrase "Ad hoc".

Ad lib adverb - Without advance preparation.

Ad hoc and ad lib are semantically related in extemporaneous topic. Sometimes you can use "Ad hoc" instead an adjective phrase "Ad lib", if it concerns topics such as unrehearsed, improvised.