Source : Webster's Revised Unabridged Dictionary (1913)

Plodder \Plod"der\, n.
   One who plods; a drudge.

Source : WordNet®

plodder
     n 1: someone who walks in a laborious heavy-footed manner [syn: {trudger},
           {slogger}]
     2: someone who works slowly and monotonously for long hours
        [syn: {slogger}]
     3: someone who moves slowly; "in England they call a slowpoke a
        slowcoach" [syn: {slowpoke}, {stick-in-the-mud}, {slowcoach}]