The Collaborative International Dictionary of English v.0.48:

Aftermath \Aft"er*math\, n. [After + math. See Math.]
   A second moving; the grass which grows after the first crop
   of hay in the same season; rowen. --Holland.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aftermath
    n 1: the consequences of an event (especially a catastrophic
         event); "the aftermath of war"; "in the wake of the
         accident no one knew how many had been injured" [syn:
         aftermath, wake, backwash]
    2: the outcome of an event especially as relative to an
       individual [syn: consequence, aftermath]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "aftermath":
   afterbirth, afterclap, aftercrop, aftereffect, afterglow,
   aftergrowth, afterimage, afterpain, aftertaste, bearing,
   bumper crop, by-product, causation, conclusion, consequence, crop,
   descendant, dynasty, effect, event, eventuality, fruit, harvest,
   heir, issue, line, lineage, make, offspring, outcome, output,
   placenta, posterity, proceeds, produce, product, production,
   remainder, residual, residuum, result, second crop, secundines,
   sequel, side effect, successor, track, trail, vintage, wake,
   yield



Bouvier's Law Dictionary, Revised 6th Ed (1856):

AFTERMATH. A right to have the last crop of grass or pasturage. 1 Chit. Pr.
181.