The Collaborative International Dictionary of English v.0.48:

Duress \Du*ress"\, v. t.
   To subject to duress. "The party duressed." --Bacon.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Duress \Du"ress\, n. [OF. duresse, du?, hardship, severity, L.
   duritia, durities, fr. durus hard. See Dure.]
   1. Hardship; constraint; pressure; imprisonment; restraint of
      liberty.
      [1913 Webster]

            The agreements . . . made with the landlords during
            the time of slavery, are only the effect of duress
            and force.                            --Burke.
      [1913 Webster]

   2. (Law) The state of compulsion or necessity in which a
      person is influenced, whether by the unlawful restrain of
      his liberty or by actual or threatened physical violence,
      to incur a civil liability or to commit an offense.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

108 Moby Thesaurus words for "duress":
   amperage, argumentum baculinum, armipotence, authority, beef,
   black power, brute force, captivity, charge, charisma,
   close arrest, clout, coercion, cogence, cogency, compulsion,
   compulsoriness, confinement, constraint, detention, dint, drive,
   durance, durance vile, effect, effectiveness, effectuality, energy,
   flower power, force, force majeure, forcefulness, full blast,
   full force, high pressure, house arrest, immuration, immurement,
   imprisonment, incarceration, influence, internment, intimidation,
   jailing, main force, main strength, mana, mandatedness,
   mandatoriness, might, might and main, mightiness, moxie,
   muscle power, necessariness, necessitation, necessitude, necessity,
   obligation, obligatoriness, obligement, pizzazz, poop, potence,
   potency, potentiality, power, power pack, power structure,
   power struggle, powerfulness, prepotency, pressure, productiveness,
   productivity, puissance, pull, punch, push, restraint, sinew,
   steam, strength, strong arm, strong-arm tactics, superiority,
   superpower, term of imprisonment, the big stick, the bludgeon,
   the club, the jackboot, the mailed fist, the strong arm, the sword,
   threat, throughout, validity, vehemence, vigor, vim, violence,
   virility, virtue, virulence, vitality, wattage, weight