The Collaborative International Dictionary of English v.0.48:

Encounter \En*coun"ter\, v. t. [imp. & p. p. Encountered; p.
   pr. & vb. n. Encountering.] [OF. encontrer; pref. en- (L.
   in) + contre against, L. contra. See Counter, adv.]
   To come against face to face; to meet; to confront, either by
   chance, suddenly, or deliberately; especially, to meet in
   opposition or with hostile intent; to engage in conflict
   with; to oppose; to struggle with; as, to encounter a friend
   in traveling; two armies encounter each other; to encounter
   obstacles or difficulties, to encounter strong evidence of a
   truth.
   [1913 Webster]

         Then certain philosophers of the Epicureans, and of the
         Stoics, encountered him.                 --Acts xvii.
                                                  18.
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         I am most fortunate thus accidentally to encounter you.
                                                  --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Encounter \En*coun"ter\, v. i.
   To meet face to face; to have a meeting; to meet, esp. as
   enemies; to engage in combat; to fight; as, three armies
   encountered at Waterloo.
   [1913 Webster]

         I will encounter with Andronicus.        --Shak.
   [1913 Webster]

         Perception and judgment, employed in the investigation
         of all truth, have in the first place to encounter with
         particulars.                             --Tatham.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Encounter \En*coun"ter\, n. [OF. encontre, fr. encontrer. See
   Encounter, v. t.]
   1. A meeting face to face; a running against; a sudden or
      incidental meeting; an interview.
      [1913 Webster]

            To shun the encounter of the vulgar crowd. --Pope.
      [1913 Webster]

   2. A meeting, with hostile purpose; hence, a combat; a
      battle; as, a bloody encounter.
      [1913 Webster]

            As one for . . . fierce encounters fit. --Spenser.
      [1913 Webster]

            To join their dark encounter in mid-air. --Milton
      .

   Syn: Contest; conflict; fight; combat; assault; rencounter;
        attack; engagement; onset. See Contest.
        [1913 Webster]

WordNet (r) 3.0 (2006):

encounter
    n 1: a minor short-term fight [syn: brush, clash,
         encounter, skirmish]
    2: a casual or unexpected convergence; "he still remembers their
       meeting in Paris"; "there was a brief encounter in the
       hallway" [syn: meeting, encounter]
    3: a casual meeting with a person or thing [syn: encounter,
       coming upon]
    4: a hostile disagreement face-to-face [syn: confrontation,
       encounter, showdown, face-off]
    v 1: come together; "I'll probably see you at the meeting"; "How
         nice to see you again!" [syn: meet, run into,
         encounter, run across, come across, see]
    2: come upon, as if by accident; meet with; "We find this idea
       in Plato"; "I happened upon the most wonderful bakery not
       very far from here"; "She chanced upon an interesting book in
       the bookstore the other day" [syn: find, happen,
       chance, bump, encounter]
    3: be beset by; "The project ran into numerous financial
       difficulties" [syn: run into, encounter]
    4: experience as a reaction; "My proposal met with much
       opposition" [syn: meet, encounter, receive]
    5: contend against an opponent in a sport, game, or battle;
       "Princeton plays Yale this weekend"; "Charlie likes to play
       Mary" [syn: meet, encounter, play, take on]

Moby Thesaurus II by Grady Ward, 1.0:

210 Moby Thesaurus words for "encounter":
   Olympic games, Olympics, accost, action, advance, affront,
   alight upon, altercation, approach, appropinquate, approximate,
   appulse, argument, assail, bang, bang into, battle, be exposed to,
   be subjected to, bear down on, bear down upon, bear up,
   blunder upon, bout, brave, breast, bring before, bring forward,
   bring to bay, bring up, brunt, brush, bulldozing, bulling, bump,
   bump into, cannon, carambole, carom, carom into, challenge,
   chance upon, clash, clash with, close, close in, close with,
   collide, collision, collision course, come, come across,
   come among, come closer, come forward, come into collision,
   come near, come on, come up, come up against, come upon,
   competition, concours, concuss, concussion, conflict, confront,
   confront each other, confront with, confrontation, contend with,
   contention, contest, crack up, crack-up, crash, crash into,
   cross swords with, crump, crunch, dare, dash into, defy, derby,
   disagreement, discover serendipitously, dispute, draw near,
   draw nigh, duel, endure, engage, engagement, envisage, experience,
   face, face with, fall across, fall among, fall foul of,
   fall in with, fall upon, feel, fight, fight hand-to-hand, foul,
   fray, front, gain upon, game, games, go, go through, grapple with,
   gymkhana, hammering, happen upon, have, hit, hit against, hit upon,
   hurt, hurtle, impact, impinge, impingement, join, joining, joust,
   knock, knock against, know, labor under, lay before, light upon,
   match, matching, mauling, meet, meet head-on, meet squarely,
   meet up with, meet with, meeting, narrow squeak, narrow the gap,
   near, near thing, near-miss, onslaught, pass through, pay, percuss,
   percussion, pitch upon, place before, present to, proximate,
   put it to, quarrel, rally, ramming, rencontre, run, run across,
   run into, run smack into, run up against, run upon, run-in, scrap,
   set before, set-to, shock, sideswipe, sidle up to, skirmish,
   slam into, sledgehammering, smack into, smash, smash into,
   smash up, smash-up, smashing, spend, stand under, stem, step up,
   strike, strike against, struggle, stumble on, stumble upon, suffer,
   sustain, take on, taste, test, thrusting, tilt, tournament,
   tourney, trial, tumble on, turn up, undergo, war, whomp,
   wrestle with