extemporaneous
ek-stem-puh-RAY-nee-usadjMeaning spoken or done without any preparation
Memory hook EX TEMPOR: OUT of the moment. Asked to speak with no warning, Grandpa Gus stands right up and talks with no notes at all, straight out of the moment. His speech is extemporaneous.
Called on without warning, Dev gave an extemporaneous talk about his favorite book.
In context Most of the toasts had been written weeks ahead, but the best one was extemporaneous: the bride’s grandfather simply stood up and spoke from the heart.
Similar impromptu, unrehearsed, spontaneous, off-the-cuff
Opposite rehearsed, prepared, planned
From Late Latin extemporaneus, from the Latin phrase ex tempore, “out of the moment.”