plod 
(pl
ŏd)
v. plod·ded, plod·ding, plods
v.intr.1. To move or walk heavily or laboriously; trudge: "donkeys that plodded wearily in a circle round a gin" (D.H. Lawrence).
2. To work or act perseveringly or monotonously; drudge: plodding through a mountain of paperwork.
v.tr. To trudge along or over.
n.1. The act of moving or walking heavily and slowly.
2. The sound made by a heavy step.
[Perhaps imitative.]
plodder n.
plodding·ly adv.