A new moon is the moon when it first appears as a thin curved shape at the start of its four-week cycle. Thenew moon is also the time of the month when the moon appears in this way.
...the pale crescent of a new moon.
The new moon was the occasion of festivals of rejoicing in Egypt.
new moon in British English
noun
1.
the moon when it appears as a narrow waxing crescent
2.
the time at which this occurs
3. astronomy
one of the four principal phases of the moon, occurring when it lies between the earth and the sun
new moon in American English
1.
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