noun
the first fourth of the Moon's period of revolution around the Earth
• Hypernyms: ↑half-moon
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Astron.
the instant, approximately one week after a new moon, when one half of the moon's disk is illuminated by the sun. See diag. under moon.
[1905-10]
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first quarter,
1. the period of time between the new moon and the first half moon.
2. the phase of moon represented by the first half moon after the new moon.
3. the first fourth of any period of time; the first quarter of the year.
Useful english dictionary. 2012.