From WordNet (r) 3.0 (2006):
slog
v 1: work doggedly or persistently; "She keeps plugging away at
her dissertation" [syn: plug away, peg away, slog,
keep one's nose to the grindstone, keep one's shoulder
to the wheel]
2: walk heavily and firmly, as when weary, or through mud;
"Mules plodded in a circle around a grindstone" [syn: slog,
footslog, plod, trudge, pad, tramp]
3: strike heavily, especially with the fist or a bat; "He
slugged me so hard that I passed out" [syn: slug, slog,
swig]