(1):

(v. i.) To be multiplied by four; to increase fourfold; to become four times as much.

(2):

(v. t.) To multiply by four; to increase fourfold; to double; to double twice.

(3):

(n.) four times the sum or number; a fourfold amount; as, to receive to quadruple of the amount in damages.

(4):

(a.) Fourfold; as, to make quadruple restitution; a quadruple alliance.