The Collaborative International Dictionary of English v.0.48:

Plodding \Plod"ding\, a.
   Progressing in a slow, toilsome manner; characterized by
   laborious diligence; as, a plodding peddler; a plodding
   student; a man of plodding habits. --Plod"ding*ly, adv.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plod \Plod\, v. i. [imp. & p. p. Plodded; p. pr. & vb. n.
   Plodding.] [Gf. Gael. plod a clod, a pool; also, to strike
   or pelt with a clod or clods.]
   1. To travel slowly but steadily; to trudge. --Shak.
      [1913 Webster]

   2. To toil; to drudge; especially, to study laboriously and
      patiently. "Plodding schoolmen." --Drayton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

plodding
    adj 1: (of movement) slow and laborious; "leaden steps" [syn:
           leaden, plodding]
    n 1: hard monotonous routine work [syn: drudgery, plodding,
         grind, donkeywork]
    2: the act of walking with a slow heavy gait; "I could recognize
       his plod anywhere" [syn: plodding, plod]