Source : Webster's Revised Unabridged Dictionary (1913)

Mountain specter \Moun"tain spec"ter\
   An optical phenomenon sometimes seen on the summit of
   mountains (as on the Brocken) when the observer is between
   the sun and a mass of cloud. The figures of the observer and
   surrounding objects are seen projected on the cloud, greatly
   enlarged and often encircled by rainbow colors.