An incantation is a chant or formulaic use of words invoking or suggesting magic or ritual.

From A Poet’s Glossary

The following additional definition of the term incantation is reprinted from A Poet's Glossary by Edward Hirsch.

A formulaic use of words to create magical effects. Incantation derives from a Latin word meaning “to consecrate with charms or spells,” and, indeed, charms, spells, chants, and conjurations all employ the apparatus of sympathetic magic. Incantations, whether spoken or chanted, are characteristic of archaic poetries everywhere, which have always employed the rudimentary power of repetition to create enchantment. Oracular and prophetic poets rely on what Roman Jakobson calls “the magic, incantatory function” of language to raise words beyond speech, to create dream states and invoke apocalyptic forces, dangerous transcendent powers. The Orphic poets and Hebrew prophets, as well as those outsize vatic figures who identify with them (Christopher SmartWilliam BlakeWalt WhitmanRobert Desnos), deliver incantations formally, not haphazardly, and harness the rhythmic power of repetition through parallel structures and catalogs. Here is a statement from “The Song of Amergin,” which was said, as Robert Graves has pointed out, to have been chanted by the chief bard of the Milesian invaders as he set his foot on the soil of Ireland, in the year of the world 2736 (1268 BCE).

     Invoke, People of the Sea, invoke the poet, that he may
        compose a spell for you.
     For I, the Druid, who set out letters in Ogham, I, who part
     I will approach the rath of the Sidhe to seek a cunning poet
        that together we may concoct incantations.
     I am a wind of the sea.

Read more from this collection.