Double \Dou"ble\, v. t. [imp. & p. p. Doubled; p. pr. & vb. n. Doubling.]

[OE. doblen, dublen, doublen, F. doubler, fr. L. duplare, fr. duplus. See Double, a.]

1. To increase by adding an equal number, quantity, length, value, or the like; multiply by two; to double a sum of money; to double a number, or length.

Double six thousand, and then treble that. --Shak.

2. To make of two thicknesses or folds by turning or bending together in the middle; to fold one part upon another part of; as, to double the leaf of a book, and the like; to clinch, as the fist; -- often followed by up; as, to double up a sheet of paper or cloth.

Source: Webster's Revised Unabridged Dictionary (1913)