Definition of "ad-lib" []

• To improvise and deliver extemporaneously. (verb-transitive)
• To engage in improvisation, as during delivery of a speech. (verb-intransitive)
• Words, music, or actions uttered, performed, or carried out extemporaneously. (noun)
• Uttered, performed, or carried out spontaneously. See Synonyms at extemporaneous. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "He tried his trademark joking, sputtering an ad-lib about eating too much barbecue but his head bobbed under the strain, and his thin neck muscles stretched and strained in the light."
• "There was always room to ad-lib lines with the court and each other, but we all knew where we were going, and what was supposed to happen on the field."
• "When Fred refused to change the script to accommodate me, or even to allow me to rewrite it, the director said that I could ad-lib some lines that were not as sexually debasing as what was on the page in a scene with the actor who was portraying my husband, the amazing Mr. Gary Busey."