Morning Terminator(glossary entry)
The Moon's terminator makes a complete circle around the Moon's globe. However, along one half of this arc the passage of the terminator brings sunlight, and on the other half it brings darkness. The Morning Terminator is the arc along which the Sun is rising. The arc along which the Sun is setting is referred to as the Evening Terminator. - Jim Mosher
See also: Saber's Beads, which is a curious optical phenomenon related to the very young (and extremely thin) moon's crescent. During the appearance of Saber's Beads, the location of the Morning Terminator is very near the moon's eastern limb (only a couple of hours after New Moon). Saber's Beads are also observable at the very OLD moon's crescent, shortly before New Moon (the Evening Terminator near the moon's WESTERN limb). - DannyCaes Feb 12, 2008
All books about the moon and lunar observing.