Definition of superarctic in US English:

superarctic

noun

rare, historical
  • (In the terminology of H. C. Watson) designating a zone of vegetation occurring above the heather line, which forms one of six such zones in the British Isles and is characteristic of the highest areas of Scotland.

Origin

Mid 19th century; earliest use found in Hewett Watson (1804–1881), botanist and phrenologist.