The Collaborative International Dictionary of English v.0.48:

Triangle \Tri"an`gle\, n. [L. triangulum, fr. triangulus
   triangular; tri- (see Tri-) + angulus angle: cf. F.
   triangle. See Angle a corner.]
   1. (Geom.) A figure bounded by three lines, and containing
      three angles.
      [1913 Webster]

   Note: A triangle is either plane, spherical, or curvilinear,
         according as its sides are straight lines, or arcs of
         great circles of a sphere, or any curved lines
         whatever. A plane triangle is designated as scalene,
         isosceles, or equilateral, according as it has no two
         sides equal, two sides equal, or all sides equal; and
         also as right-angled, or oblique-angled, according as
         it has one right angle, or none; and oblique-angled
         triangle is either acute-angled, or obtuse-angled,
         according as all the angles are acute, or one of them
         obtuse. The terms scalene, isosceles, equilateral,
         right-angled, acute-angled, and obtuse-angled, are
         applied to spherical triangles in the same sense as to
         plane triangles.
         [1913 Webster]

   2. (Mus.) An instrument of percussion, usually made of a rod
      of steel, bent into the form of a triangle, open at one
      angle, and sounded by being struck with a small metallic
      rod.
      [1913 Webster]

   3. A draughtsman's square in the form of a right-angled
      triangle.
      [1913 Webster]

   4. (Mus.) A kind of frame formed of three poles stuck in the
      ground and united at the top, to which soldiers were bound
      when undergoing corporal punishment, -- now disused.
      [1913 Webster]

   5. (Astron.)
      (a) A small constellation situated between Aries and
          Andromeda.
      (b) A small constellation near the South Pole, containing
          three bright stars.
          [1913 Webster]

   Triangle spider (Zool.), a small American spider
      (Hyptiotes Americanus) of the family Ciniflonidae,
      living among the dead branches of evergreen trees. It
      constructs a triangular web, or net, usually composed of
      four radii crossed by a double elastic fiber. The spider
      holds the thread at the apex of the web and stretches it
      tight, but lets go and springs the net when an insect
      comes in contact with it.
      [1913 Webster]

WordNet (r) 3.0 (2006):

triangle
    n 1: a three-sided polygon [syn: triangle, trigon,
         trilateral]
    2: something approximating the shape of a triangle; "the
       coastline of Chile and Argentina and Brazil forms two legs of
       a triangle"
    3: a small northern constellation near Perseus between Andromeda
       and Aries [syn: Triangulum, Triangle]
    4: any of various triangular drafting instruments used to draw
       straight lines at specified angles
    5: a percussion instrument consisting of a metal bar bent in the
       shape of an open triangle

Moby Thesaurus II by Grady Ward, 1.0:

176 Moby Thesaurus words for "triangle":
   Platonic body, T square, acute-angled triangle, adulterous affair,
   adultery, affair, amour, battery, bell, bells, bones, branks,
   castanets, celesta, chime, chimes, church bell, clapper, clappers,
   clover, cowbell, crank, crash cymbal, cube, cuboid, cucking stool,
   cuckoldry, cusp, cymbals, decagon, deuce-ace, dinner bell,
   dinner gong, dodecagon, dodecahedron, doorbell, ducking stool,
   entanglement, equilateral triangle, eternal triangle,
   finger cymbals, finger pillory, fire bell, flirtation,
   forbidden love, foursquare, gamelan, glockenspiel, gnomon, gong,
   gong bell, hand bell, handbells, hanky-panky, heptagon, hexagon,
   hexahedron, hypercube, icosahedron, idiophone, illicit love,
   infidelity, intrigue, isosceles triangle, jingle bell, leash,
   liaison, love affair, lyra, maraca, marimba, metallophone, oblong,
   obtuse-angled triangle, octagon, octahedron, orchestral bells,
   oxygon, parallelepiped, parallelogram, passing bell, pentagon,
   pentahedron, percussion, percussion instrument, percussions,
   percussive, pillory, polygon, polyhedron, prism, prismoid, pyramid,
   quadrangle, quadrant, quadrature, quadrilateral, rattle,
   rattlebones, rectangle, rhombohedron, rhomboid, rhombus, romance,
   romantic tie, rule, ruler, sacring bell, set of three, shamrock,
   sheepbell, sizzler, sleigh bell, snappers, square, stocks,
   straightedge, tam-tam, telephone bell, tercet, ternary, ternion,
   terzetto, tetragon, tetragram, tetrahedron, three, threesome,
   tierce, tintinnabula, tintinnabulum, tongue, tonitruone, trapeze,
   trapezium, trapezoid, treadmill, trebuchet, trefoil, trey, triad,
   trialogue, triangles, tricorn, trident, triennium, trihedron,
   trilateral, trilogy, trimester, trine, trinity, trinomial, trio,
   triphthong, triple crown, triple threat, triplet, triplopy, tripod,
   triptych, trireme, triseme, triskelion, trisul, triumvirate,
   triunity, trivet, troika, tubular bells, unfaithfulness, vibes,
   vibraphone, whipping post, wooden horse, xylophone



U.S. Gazetteer Places (2000):

Triangle, VA -- U.S. Census Designated Place in Virginia
   Population (2000):    5500
   Housing Units (2000): 2318
   Land area (2000):     2.633489 sq. miles (6.820706 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    2.633489 sq. miles (6.820706 sq. km)
   FIPS code:            79360
   Located within:       Virginia (VA), FIPS 51
   Location:             38.551287 N, 77.325900 W
   ZIP Codes (1990):     22172
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Triangle, VA
    Triangle