noun

• (uncountable, Canada, US) Coarse woody debris; deadwood.
  "Heaver forest growth on the north-facing slopes, together with considerable deadfall and soil cover, makes geologic interpretation there difficult."
• (uncountable, Canada, US) Coarse woody debris; deadwood.
  "A fifth negative test pit was excavated near the largest creek at Middle Point. As well, the roots of all deadfalls within the corridor were examined for the presence of cultural material. Deadfalls were more common in the drier areas, especially near stream channels."
• (countable, Canada, US, hunting) A kind of trap for animals, consisting of a heavy board or log that falls on to the prey.
  "It [the wolverine] is so cunning as rarely to enter a deadfall itself, but will carefully pull it to pieces and then eat the bait in safety. I was informed by hunters at Selkirk Settlement that they sometimes lost the successful result of several days' trapping by a single wolverine, which, following their path, would pull down every deadfall, or destroy any animal already caught."
• (countable, US, slang) A cheap, rough bar or saloon.
  "Dens of the description of the "Tapis Franc," and the "deadfalls" of San Francisco and Sacramento, are now matters of history only, and it seems beyond the bounds of probability that similar haunts of vice, and the brutal and lawless scenes there enacted, will ever again be permitted to disgrace our country, and the name of civilization."