improvise

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To invent, compose, or perform with little or no preparation.
2. v. To play or sing (music) extemporaneously, especially by inventing variations on a melody or creating new melodies in accordance with a set progression of chords.
3. v. To make or provide from available materials: improvised a dinner from what I found in the refrigerator.
4. v. To invent, compose, or perform something extemporaneously.
5. v. To improvise music.
6. v. To make do with whatever materials are at hand.

Century Dictionary and Cyclopedia

1. To compose and recite or sing without premeditation; speak or perform extemporaneously, especially verse or music.
2. To do or perform anything on the spur of the moment for a special occasion; contrive or bring about in an offhand way.
3. To compose verses or music extemporaneously; hence, to do anything on the spur of the moment or in an offhand way.

Wiktionary

1. v. To make something up or invent it as one goes on; to proceed guided only by imagination, instinct, and guesswork rather than by a careful plan.

GNU Webster's 1913

1. v. To compose, recite, or sing extemporaneously, especially in verse; to extemporize; also, to play upon an instrument, or to act, extemporaneously.
2. v. To bring about, arrange, do, or make, immediately or on short notice, without previous preparation and with no known precedent as a guide.
3. v. To invent, or provide, offhand, or on the spur of the moment.
4. v. To produce or render extemporaneous compositions, especially in verse or in music, without previous preparation; hence, to do anything offhand.

WordNet 3.0

1. v. perform without preparation
2. v. manage in a makeshift way; do with whatever is at hand