WordNet (r) 3.0 (2006):

mow down
    v 1: kill a large number of people indiscriminately; "The Hutus
         massacred the Tutsis in Rwanda" [syn: massacre,
         slaughter, mow down]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "mow down":
   beat down, blow down, blow over, bowl down, bowl over, break down,
   bring down, bulldog, bulldoze, burn down, cast down, chop down,
   cut down, dash down, deck, down, drop, fell, fetch down, flatten,
   floor, ground, hew down, knock down, knock over, lay level,
   lay low, lay out, level, precipitate, prostrate, pull down, rase,
   raze, send headlong, smash, spread-eagle, steamroller, supinate,
   take down, tear down, throw, throw down, topple, trip, tumble,
   whack down