- the first phase of the moon when it is between the earth and the sun, with its dark side toward the earth: it is followed by the waxing crescent phase
- the time of the new moon
new moonnew moon
- The phase of the moon at which the moon, as viewed from Earth, does not appear to be illuminated by the sun. The new phase marks the beginning of a single revolution of the moon around the earth.
- The period of the month when such a moon occurs.
(plural new moons)