Source : Webster's Revised Unabridged Dictionary (1913)

Emerald \Em"er*ald\, a.
   Of a rich green color, like that of the emerald. ``Emerald
   meadows.'' --Byron.

   {Emerald fish} (Zo["o]l.), a fish of the Gulf of Mexico
      ({Gobionellus oceanicus}), remarkable for the brilliant
      green and blue color of the base of the tongue; -- whence
      the name; -- called also {esmeralda}.

   {Emerald green}, a very durable pigment, of a vivid light
      green color, made from the arseniate of copper; green
      bice; Scheele's green; -- also used adjectively; as,
      emerald green crystals.

   {Emerald Isle}, a name given to Ireland on account of the
      brightness of its verdure.

   {Emerald spodumene}, or {Lithia emerald}. (Min.) See
      {Hiddenite}.

   {Emerald nickel}. (Min.) See {Zaratite}.