Dredge (drĕj), v. t. [imp. & p. p.Dredged (drĕjd); p. pr. & vb. n.Dredging.] To catch or gather with a dredge; to deepen with a dredging machine. R. Carew.
Dredging machine, a machine (commonly on a boat) used to scoop up mud, gravel, or obstructions from the bottom of rivers, docks, etc., so as to deepen them.