Definition of dragline:
(n) :
A cable, cord, or rope used to drag an object; specifically, the line of a dragline excavator that drags the bucket.
(n) :
A strong supporting line of silk produced by a spider.
(n) :
Ellipsis of dragline excavator. [Any of several very large vehicles used for lifting, especially in the process of mining: basically an excavator which drags its bucket to fill it.]