What is a foot consisting of four syllables, of which the first and last are long, and the other short (- ~ ~ -); that is, a choreus, or trochee, and an iambus united called?

choriambus — A foot consisting of four syllables, of which the first and last are long, and the other short (- ~ ~ -); that is, a choreus, or trochee, and an iambus united. (Webster's 1913.)

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