What is "chanson de geste"

Chanson de geste \Chan`son" de geste"\ [F., prop., song of history.] Any Old French epic poem having for its subject events or exploits of early French history, real or legendary, and written originally in assonant verse of ten or twelve syllables. The most famous one is the Chanson de Roland.

Langtoft had written in the ordinary measure of the later chansons de geste.
--Saintsbury. [Webster 1913 Suppl.] ||

n. Old French epic poems

The chanson de geste, Old French for "song of heroic deeds" (from gesta: Latin: "deeds, actions accomplished"), is a medieval narrative, a type of epic poem that appears at the dawn of French literature. The earliest known poems of this genre date from the late eleventh and early twelfth centuries, before the emergence of the lyric poetry of the trouvères ( troubadours) and the earliest verse romances. They reached their apogee in the period 1150–1250.

Composed in verse, these narrative poems of moderate length (averaging 4000 lines) were originally sung, or (later) recited, by minstrels or jongleurs. More than one hundred chansons de geste have survived in around three hundred manuscripts that date from the 12th to the 15th century.