Spondee, Spondaic

A kind of metrical foot. A spondee is a duple foot with two stressed syllables. Although it's rare for any two adjacent syllables to receive exactly the same stress, in spondees there's no obvious stress on one syllable rather than the other. Some examples: "pen-knife," "ad hoc," "heartburn." Spondees are sometimes substituted for iambs and trochees to vary the rhythm.

From the Guide to Literary Terms by Jack Lynch.
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