Formation \For*ma"tion\, n. [L. formatio: cf. F. formation.]

1. The act of giving form or shape to anything; a forming; a shaping. --Beattie.

2. The manner in which a thing is formed; structure; construction; conformation; form; as, the peculiar formation of the heart.

3. A substance formed or deposited.

4. (Geol.)
   (a) Mineral deposits and rock masses designated with reference to their origin; as, the siliceous formation about geysers; alluvial formations; marine formations.
   (b) A group of beds of the same age or period; as, the Eocene formation.

5. (Mil.) The arrangement of a body of troops, as in a square, column, etc. --Farrow.

Source: Webster's Revised Unabridged Dictionary (1913)