Ground rhythm refers to the foundational metrical pattern that underlies a poem’s surface rhythm, providing a consistent structural backbone even when variations, substitutions, or syncopations occur; it is the "default" meter that readers intuitively sense beneath irregularities, such as the iambic pentameter in Shakespeare’s sonnets that persists despite occasional trochaic inversions or feminine endings, anchoring the poem’s musicality and enabling expressive deviation without loss of coherence.

ground rhythm: The basic, established metrical pattern or beat of a poem, which the poet may vary or play against for effect; it's the rhythmic expectation set by the first few lines; synonymous with framework beat.