The Collaborative International Dictionary of English v.0.48:

Offtake \Off"take`\, n. [Off + take.]
   1. Act of taking off; specif., the taking off or purchase of
      goods.
      [Webster 1913 Suppl.]

   2. Something taken off; a deduction.
      [Webster 1913 Suppl.]

   3. A channel for taking away air or water; also, the point of
      beginning of such a channel; a take-off.
      [Webster 1913 Suppl.]