— fourth-dimensional , adj.
1. Physics , Math. a dimension in addition to length, width, and depth, used so as to be able to employ geometrical language in discussing phenomena that depend on four variables: Time is considered a fourth dimension for locating points in space-time.
2. something beyond the kind of normal human experience that can be explained scientifically: The story deals with ESP and other excursions into the fourth dimension.
[ 1870-75 ]