Definition of mainlands:
(n) :
The continent; the principal land, as distinguished from islands or a peninsula.
(n) :
The principal island of a group.
(n) :
(Northern Ireland) Great Britain.
(n) :
The largest island in the Orkney Islands council area, to the north of Scotland.
(n) :
The largest island in the Shetland Islands council area, to the north of both Orkney and Scotland.
(n) :
(historical) A historical region of British Columbia, British North America, British Empire.