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1. adjective Of or characterized by an impromptu fashion, with little or no preparation beforehand. Jazz improv is always a bit ad-lib by design; you can't plan what you might play!
2. adverb Done in an impromptu or free-hand fashion, with little or no preparation beforehand. His comedy is always so unique; I hear he does the whole thing ad-lib.
3. noun Something, usually performative in nature, that is done with little or no preparation beforehand. His speech this morning felt like it was a bit of an ad-lib. I don't think he prepared any notes ahead of time.
4. verb To say, do, or perform something in an impromptu fashion, with little or no preparation beforehand. I had forgotten to rehearse my lines for the audition, so I just decided to ad-lib the whole way through.
an ad hoc organization or process is not planned but is formed or arranged when it is necessary for a particular purpose An ad hoc group of 75 parents is leading the protest to demand the resignation of the headteacher. He doesn't charge a set amount for his work but negotiates fees on an ad hoc basis.
if something happens or continues ad infinitum, it happens again and again in the same way, or it continues forever The TV station just shows repeats of old comedy programmes ad infinitum. Her list of complaints went on and on ad infinitum.
if someone discusses something ad nauseam, they talk about it so much that it becomes very boring She talks ad nauseam about how brilliant her children are.
For the special purpose or end at hand; also, by extension, improvised or impromptu. The term, Latin for "to this," is most often used for committees established for a specific purpose, as in The committee was formed ad hoc to address health insurance problems. The term is also used as an adjective ( An ad hoc committee was formed), and has given rise to the noun adhocism for the tendency to use temporary, provisional, or improvised methods to deal with a particular problem. [Early 1600s]
To ridiculous excess, to a sickening degree. For example, I wish he'd drop the subject; we have heard about budget cuts ad nauseam. The term, Latin for "to [the point of] nausea," has been used in English since the early 1600s.