noun.
In Irish folklore, a mischievous elflike creature or fairy who grants wishes or reveals the location of hidden treasure when captured.
the GNU version of the Collaborative International Dictionary of English
noun.
A small mischievous elf or spirit in Irish folklore; it is often depicted in literature as a dwarfish bearded old man; -- legend tells that if a leprechaun is captured, he will reveal the location of his hidden pot of gold.