Mean, a. [OE. mene, OF. meiien, F. moyen, fr. L. medianus that is in the middle, fr. medius; akin to E. mid. See Mid.] 1. Occupying a middle position; middle; being about midway between extremes.
Being of middle age and a mean stature. Sir. P. Sidney.
2. Intermediate in excellence of any kind.
According to the fittest style of lofty, mean, or lowly. Milton.
3. (Math.) Average; having an intermediate value between two extremes, or between the several successive values of a variable quantity during one cycle of variation; as, mean distance; mean motion; mean solar day.
Mean distance (of a planet from the sun) (Astron.), the average of the distances throughout one revolution of the planet, equivalent to the semi-major axis of the orbit. — Mean error(Math. Phys.), the average error of a number of observations found by taking the mean value of the positive and negative errors without regard to sign. — Mean-square error, orError of the mean square(Math. Phys.), the error the square of which is the mean of the squares of all the errors; — called also, especially by European writers, mean error. — Mean line. (Crystallog.) Same as Bisectrix. — Mean noon, noon as determined by mean time. — Mean proportional (between two numbers) (Math.), the square root of their product. — Mean sun, a fictitious sun supposed to move uniformly in the equator so as to be on the meridian each day at mean noon. — Mean time, time as measured by an equable motion, as of a perfect clock, or as reckoned on the supposition that all the days of the year are of a mean or uniform length, in contradistinction from apparent time, or that actually indicated by the sun, and from sidereal time, or that measured by the stars.