What does "limerick" mean?

Limerick: A nonsense poem of five anapestic lines, of which lines 1, 2, and 5 are of there feet, and rime, and lines 3 and 4 are of two feet, and rime; as -- There was a young lady, Amanda, Whose Ballades Lyriques were quite fin de Siècle, I deem But her Journal Intime Was what sent her papa to Uganda.

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