The Collaborative International Dictionary of English v.0.48:

Trespass \Tres"pass\, v. i. [imp. & p. p. Trespassed; p. pr. &
   vb. n. Trespassing.] [OF. trespasser to go across or
   over, transgress, F. tr['e]passer to die; pref. tres- (L.
   trans across, over) + passer to pass. See Pass, v. i., and
   cf. Transpass.]
   1. To pass beyond a limit or boundary; hence, to depart; to
      go. [Obs.]
      [1913 Webster]

            Soon after this, noble Robert de Bruce . . .
            trespassed out of this uncertain world. --Ld.
                                                  Berners.
      [1913 Webster]

   2. (Law) To commit a trespass; esp., to enter unlawfully upon
      the land of another.
      [1913 Webster]

   3. To go too far; to put any one to inconvenience by demand
      or importunity; to intrude; as, to trespass upon the time
      or patience of another.
      [1913 Webster]

   4. To commit any offense, or to do any act that injures or
      annoys another; to violate any rule of rectitude, to the
      injury of another; hence, in a moral sense, to transgress
      voluntarily any divine law or command; to violate any
      known rule of duty; to sin; -- often followed by against.
      [1913 Webster]

            In the time of his distress did he trespass yet more
            against the Lord.                     --2 Chron.
                                                  xxviii. 22.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trespassing
    adj 1: gradually intrusive without right or permission; "we
           moved back from the encroaching tide"; "invasive
           tourists"; "trespassing hunters" [syn: encroaching(a),
           invasive, trespassing(a)]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "trespassing":
   adoption, appropriation, arrogation, assumption, breach of law,
   contravention, encroachment, entrance, entrenchment, impingement,
   imposition, incursion, infiltration, influx, infraction,
   infringement, injection, inroad, insinuation, interference,
   interjection, interloping, interposition, interposure,
   interruption, intervention, intrusion, invasion, irruption,
   lawbreaking, obtrusion, playing God, seizure, transgression,
   trespass, unlawful entry, usurpation, violation of law