2 Answers

Learn here>>http://earthsky.org/moon-phases/waning-crescent

What is a waning crescent moon? The waning crescent moon, sometimes called an old moon, is defined to occur when the Moon is nearly, but not precisely, on a line with the Earth and Sun. This means that part but less than one-half of the Moon is illuminated by direct sunlight, creating a crescent moon. Because the fraction of the Moon’s disk that is illuminated is decreasing, we consider the Moon to be “waning.” Each new lunar cycle is measured beginning at each new moon and the waning crescent moon occurs when the Moon is more than three-quarters of the way around the sky (i.e., along its orbit) from new moon.

More here>>http://fullmoonphases.com/waning-crescent-moon/

waning means it's getting smaller 

waxing means it's getting larger

That was the quick answer