spoken or performed without practicing or preparing

unrehearsed, improvised

to think out, invent (a plan etc)

conceive, dream up

without preparation

unrehearsed, improvised

to compose music, words etc during the performance; to provide, make or do (something) quickly, using whatever happens to be available

make up

(of a person, behaviour) acting on, resulting from an impulse

tending to act without thought

to make or design (something not existing before); to make up, think of, (something) for the first time

create, think up

done, happening, from feelings, not suggested or planned

impulsive, willing

instinctively

instinctively

not prepared or ready

not ready

(of an answer, action) not said, done etc as the result of a hint, suggestion etc

tending to act without thought