ad-lib

(r) without advance preparation
- he spoke ad lib
ad libitum, impromptu, spontaneously,
(s) with little or no preparation or forethought
- his ad-lib comments showed poor judgment
- an extemporaneous piano recital
- an extemporary lecture
- an extempore skit
- an impromptu speech
- offhand excuses
- trying to sound offhanded and reassuring
- an off-the-cuff toast
- a few unrehearsed comments
extemporaneous, extemporary, extempore, impromptu, offhand, offhanded, off-the-cuff, unrehearsed,
(s) said or done without having been planned or written in advance
- he made a few ad-lib remarks
spontaneous, unwritten,

(n) remark made spontaneously without prior preparation
- his ad-libs got him in trouble with the politicians

(v) perform without preparation
- he extemporized a speech at the wedding
extemporise, improvise, improvize, extemporize,

ad libitum impromptu spontaneously extemporaneous extemporary extempore offhand offhanded off-the-cuff unrehearsed extemporise improvise improvize extemporize spontaneous unwritten

ad libitum