The Collaborative International Dictionary of English v.0.48:

Tryst \Tryst\, n. [OE. trist, tryst, a variant of trust; cf.
   Icel. treysta to make trusty, fr. traust confidence,
   security. See Trust, n.]
   1. Trust. [Obs.]
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   2. An appointment to meet; also, an appointed place or time
      of meeting; as, to keep tryst; to break tryst. [Scot. or
      Poetic]
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   To bide tryst, to wait, at the appointed time, for one with
      whom a tryst or engagement is made; to keep an engagement
      or appointment.
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            The tenderest-hearted maid
            That ever bided tryst at village stile. --Tennyson.
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