echelon

echelon is a Noun

Definition:

[1] An arrangement of a body of troops when its divisions are drawn up in parallel lines each to the right or the left of the one in advance of it, like the steps of a ladder in position for climbing. Also used adjectively; as, echelon distance. Upton (Tactics).

[2] An arrangement of a fleet in a wedge or Encyc. Dict. Echelon lens (Optics), a large lens constructed in several parts or layers, extending in a succession of annular rings beyond the central lens; - - used in lighthouses.