Definition of: echelon

(esh′ə·lon) noun
1. A staggered troop, fleet, or airplane formation, one rank, ship, or airplane behind the other, but extending farther toward one flank than the preceding rank, ship, or airplane: often V-shaped.
2. Mil. a One of the different fractions of a command arranged from front to rear, to which a particular combat mission is assigned: assault echelon, support echelon. b One of the various subdivisions from front to rear of a military headquarters: forward echelon, rear echelon. c A military unit regarded as having a distinct function: command echelon, first echelon maintenance, etc.
3. Optics A diffraction grating made of glass plates so constructed that each overlaps the one below, forming a stairlike pattern.
—v.t. & v.i. To form in echelon. [<F échelon <échelle ladder <L scala]
ECHELON (def. 1)