ad-lib

at one's pleasure

Synonyms: according to pleasure, ad libitum, as one thinks best, as one wishes, at will, extemporaneous, extempore, extemporize, extemporized, impromptu, improvise, improvised, made-up, off-the-cuff, off-the-cuff, spontaneous, unprepared, unrehearsed, without restraint

Antonyms: deliberate, planned, prepared, rehearsed, written

in an improvised manner

Synonyms: extemporaneously, extempore, impromptu, off the cuff, off the top of one’s head, spontaneously, without preparation, without rehearsal

Antonyms: deliberately, planned, prepared, rehearsed, written

improvise speech

Synonyms: extemporize, invent, make up, speak extemporaneously, speak impromptu, speak off the cuff

Antonyms: plan, prepare, rehearse, write

Say what's in the play and don't ad-lib.

His ad-libs were very funny.