A Limerick was once so well-written that the muse AND her dog were both smitten. The poor dog had to *** - and he sniffed round my tree but my rhyme was unbarked and unbitten.
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The defining "foot" of a limerick's meter is usually the anapaest, (ta-ta-TUM), but catalexis (missing a weak syllable at the beginning of a line) and extra-syllable rhyme (which adds an extra unstressed syllable) can make limericks appear amphibrachic (ta-TUM-ta).