The Collaborative International Dictionary of English v.0.48:

Gaelic \Gael"ic\ (?; 277), a. [Gael. G[`a]idhealach, Gaelach,
   from G[`a]idheal, Gael, a Scotch Highlander.] (Ethnol.)
   Of or pertaining to the Gael, esp. to the Celtic Highlanders
   of Scotland; as, the Gaelic language.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gaelic \Gael"ic\, n. [Gael. Gaelig, G[`a]ilig.]
   The language of the Gaels, esp. of the Highlanders of
   Scotland. It is a branch of the Celtic.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Erse \Erse\ ([~e]rs), n. [A modification of Irish, OE. Irishe.]
   A name sometimes given to that dialect of the Celtic which is
   spoken in the Highlands of Scotland; -- called, by the
   Highlanders, Gaelic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Gaelic
    adj 1: relating to or characteristic of the Celts [syn:
           Celtic, Gaelic]
    n 1: any of several related languages of the Celts in Ireland
         and Scotland [syn: Gaelic, Goidelic, Erse]

The Free On-line Dictionary of Computing (30 December 2018):

Gaelic

   For automated test programs.  Used in military, essentially
   replaced by ATLAS.