What is "to bargain away"

Bargain \Bar"gain\, v. t. [imp. & p. p. Bargained (?); p. pr. & vb. n. Bargaining.] To transfer for a consideration; to barter; to trade; as, to bargain one horse for another.

To bargain away, to dispose of in a bargain; -- usually with a sense of loss or disadvantage; as, to bargain away one's birthright. ``The heir . . . had somehow bargained away the estate.''
--G. Eliot.