The Estampie is both a medieval dance and musical form.

There are no surviving dance manuals describing the estampie as a dance. Illuminations and paintings from the period seem to indicate that the estampie involves fairly vigorous hopping.

The estampie musical form consists of a series of verses, perhaps of different lengths, and 2 endings ("open" and "closed") (perhaps also of different lengths), which alternate. So a typical layout would be:

Verse 1, Open Ending, Verse 1, Closed Ending
Verse 2, Open Ending, Verse 2, Closed Ending

For further reading:

Timothy McGee, Medieval Instrumental Dances.