\De*scen"sion\, n. [OF. descension, L. descensio. See
{Descent}.]
The act of going downward; descent; falling or sinking;
declension; degradation.
{Oblique descension} (Astron.), the degree or arc of the
   equator which descends, with a celestial object, below the
   horizon of an oblique sphere.
{Right descension}, the degree or arc of the equator which
   descends below the horizon of a right sphere at the same
   time with the object. [Obs.]