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]

The Collaborative International Dictionary of English v.0.48:

Erse \Erse\, a.
   Of or pertaining to the Celtic race in the Highlands of
   Scotland, or to their language.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Erse
    n 1: any of several related languages of the Celts in Ireland
         and Scotland [syn: Gaelic, Goidelic, Erse]