The definition of a Crescent Moon is:
The moon as it appears in its first or last quarter, with concave and convex edges terminating in points.
The Moon is waxing in the image above. Observations during this phase of the Moon are very pleasing due to the oblique angle of the illuminating sunlight. This brings out great shadow detail in the craters and other features of the Moon. Acording to an old saying, if the Crescent Moon will "hold water", the weather will be fair.