Milit., to expand; display; extend in a line of small depth, as a division or a battalion which has been previously formed in one or more columns.Milit., to open out; extend; move so as to form a more extended front or line: as, the regiment deployed to the right.n. Milit., the expansion or opening out of a body of troops previously compacted into a column, so as to present a more extended front.To spread out, as the lower end of a valley glacier which extends out on a plain.