Source : Webster's Revised Unabridged Dictionary (1913)

Britannic \Bri*tan"nic\, a. [L. Britannicus, fr. Britannia Great
   Britain.]
   Of or pertaining to Great Britain; British; as, her Britannic
   Majesty.

Source : WordNet®

Britannic
     adj : of Britain; "Her Britannic Majesty"