the celestial orb which revolves round the earth; the satellite of the earth; a secondary planet, whose light, borrowed from the sun, is reflected to the earth, and serves to dispel the darkness of night. the diameter of the moon is 2,160 miles, its mean distance from the earth is 240,000 miles, and its mass is one eightieth that of the earth. see lunar month, under month.-a secondary planet, or satellite, revolving about any member of the solar system; as, the moons of jupiter or saturn.-the time occupied by the moon in making one revolution in her orbit; a month.-a crescentlike outwork. see half-moon.-to expose to the rays of the moon.-to act if moonstruck; to wander or gaze about in an abstracted manner.