sestette

He had wheeled round from her, carried away in the triumph and rapture of the sestette.

The Divine Fire May Sinclair 1904

You have much too great a habit of speaking of a special octave, sestette, or line.

Recollections of Dante Gabriel Rossetti Hall Caine 1892

The opening phrases of both octave and sestette are very fine; but the second quatrain and the second terzina, though with a quality of beauty, both seem somewhat to lack distinctness.

Recollections of Dante Gabriel Rossetti Hall Caine 1892

Thus the sonnet, which had been an octave of enclosed or alternate rhymes, followed by a sestette of interlaced tercets, was now changed to a series of three quatrains with differing sets of alternate rhymes in each, at the close of which the insidious couplet succeeded in establishing itself.

Elizabethan Sonnet Cycles Phillis - Licia Thomas Lodge 1889

It was a great surprise to find part of the sestette copied in the "Prose Writings" of Walt

Confessions of a Book-Lover Maurice Francis Egan 1888

Here is another link -- José de Herédia, and his jewelled and chiselled sonnets -- the "Antique Medal" with its peerless sestette, which combines the essential meanings of Keats's "Ode to a Grecian Urn."

Confessions of a Book-Lover Maurice Francis Egan 1888