Pronunciation

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Plain form
stiffen

Third-person singular
stiffens

Past tense
stiffened

Past participle
stiffened

Present participle
stiffening

  1. (intransitive) If you stiffen, you stop moving and make your muscles hard.
    The mouse stiffened when the shadow went by.
  2. (intransitive) If your muscles or joints stiffen, they become painful to move.
    By the morning after the accident, my hand had stiffened so much that I couldn't move it.
  3. (transitive) If you stiffen something, you make it stronger or harder so that it is more difficult to bend.
    We'll have to stiffen the airplane wing or it could break in flight.
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