hour angle

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The angular distance, measured westward along the celestial equator, between the celestial meridian of the observer and the hour circle passing through a celestial body.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the angular distance along the celestial equator from the observer's meridian to the hour circle of a given celestial body
• noun (astronomy) the angular distance of a celestial point measured westward along the celestial equator from the zenith crossing; the right ascension for an observer at a particular location and time of day