The Collaborative International Dictionary of English v.0.48:

Tryst \Tryst\, v. t. [OE. tristen, trysten. See Tryst, n.]
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   1. To trust. [Obs.]
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   2. To agree with to meet at a certain place; to make an
      appointment with. [Scot.] --Burns.
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The Collaborative International Dictionary of English v.0.48:

Tryst \Tryst\, v. i.
   To mutually agree to meet at a certain place. [Scot.]
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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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WordNet (r) 3.0 (2006):

tryst
    n 1: a date; usually with a member of the opposite sex [syn:
         tryst, rendezvous]
    2: a secret rendezvous (especially between lovers) [syn:
       assignation, tryst]