Unidirectional vertical wind shear
From AMS Glossary
unidirectional vertical wind shear
(Sometimes referred to as rectilinear wind shear.) The situation in which the vertical wind shear vector does not change direction with height.
Presented on a hodograph, unidirectional shear appears as a straight line. Unidirectional vertical wind shear does not always indicate unidirectional winds, since a straight-line hodograph can result from many different wind profiles.