1. a clamp for holding a metal piece, as a sheet being deep-drawn, to prevent distortion or movement.
  2. restraint or limitation short of reduction, especially on costs: a substantial holddown on military spending.

Origin of holddown

First recorded in 1885–90; noun use of verb phrase hold down
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018