Meaning of tangential motion

tangen'tial mo'tion

Pronunciation: [key]
— Astron. Astron.
  1. the component of the linear motion of a star with respect to the sun, measured along a line perpendicular to its line of sight and expressed in miles or kilometers per second. Also calledCf.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.