Octameter in poetry is a line of eight metrical feet. It is not very common in English verse. E.g.: -

Trochaic

:Once upon a midnight dreary, while I pondered, weak and weary
:Over many a quaint and curious volume of forgotten lore-
:While I nodded, nearly napping, suddenly there came a tapping
:As of some one gently rapping, rapping at my chamber door
:(Edgar Allan Poe,

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