a Euclidean space of dimension greater than three.
Origin of hyperspace
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
maths space having more than three dimensions: often used to describe a multi-dimensional environment
(in science fiction) a theoretical dimension within which conventional space-time relationship does not apply
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Online Etymology Dictionary, © 2010 Douglas Harper