The Collaborative International Dictionary of English v.0.48:

Jackass \Jack"ass`\, n. [2d jack + ass.]
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   1. The male ass; a donkey.
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   2. A conceited dolt; a perverse blockhead; -- disparaging and
      offensive.
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   Jackass bark (Naut.), a three-masted vessel, with only the
      foremast square-rigged; a barkentine.

   Jackass deer (Zool.), the koba.

   Jackass hare, Jackass rabbit (Zool.). See Jack rabbit,
      under 2d Jack, n.

   Jackass penguin (Zool.), any species of penguin of the
      genus Spheniscus, of which several are known. One
      species (Spheniscus demersus) inhabits the islands near
      the Cape of Good Hope; another (Spheniscus Magellanicus)
      is found at the Falkland Islands. They make a noise like
      the braying of an ass; -- hence the name.

   Laughing jackass. (Zool.) See under Laughing.
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