Source : Webster's Revised Unabridged Dictionary (1913)

Plunge \Plunge\, v. t. [imp. & p. p. {Plunged}; p. pr. & vb. n.
   {Plunging}.] [OE. ploungen, OF. plongier, F. plonger, fr.
   (assumed) LL. plumbicare, fr. L. plumbum lead. See {Plumb}.]
   1. To thrust into water, or into any substance that is
      penetrable; to immerse; to cause to penetrate or enter
      quickly and forcibly; to thrust; as, to plunge the body
      into water; to plunge a dagger into the breast. Also used
      figuratively; as, to plunge a nation into war. ``To plunge
      the boy in pleasing sleep.'' --Dryden.

            Bound and plunged him into a cell.    --Tennyson.

            We shall be plunged into perpetual errors. --I.
                                                  Watts.

   2. To baptize by immersion.

   3. To entangle; to embarrass; to overcome. [Obs.]

            Plunged and graveled with three lines of Seneca.
                                                  --Sir T.
                                                  Browne.

Plunge \Plunge\, v. i.
   1. To thrust or cast one's self into water or other fluid; to
      submerge one's self; to dive, or to rush in; as, he
      plunged into the river. Also used figuratively; as, to
      plunge into debt.

            Forced to plunge naked in the raging sea. --Dryden.

            To plunge into guilt of a murther.    --Tillotson.

   2. To pitch or throw one's self headlong or violently
      forward, as a horse does.

            Some wild colt, which . . . flings and plunges.
                                                  --Bp. Hall.

   3. To bet heavily and with seeming recklessness on a race, or
      other contest; in an extended sense, to risk large sums in
      hazardous speculations. [Cant]

   {Plunging fire} (Gun.), firing directed upon an enemy from an
      elevated position.

Plunge \Plunge\, n.
   1. The act of thrusting into or submerging; a dive, leap,
      rush, or pitch into, or as into, water; as, to take the
      water with a plunge.

   2. Hence, a desperate hazard or act; a state of being
      submerged or overwhelmed with difficulties. [R.]

            She was brought to that plunge, to conceal her
            husband's murder or accuse her son.   --Sir P.
                                                  Sidney.

            And with thou not reach out a friendly arm, To raise
            me from amidst this plunge of sorrows? --Addison.

   3. The act of pitching or throwing one's self headlong or
      violently forward, like an unruly horse.

   4. Heavy and reckless betting in horse racing; hazardous
      speculation. [Cant]

   {Plunge bath}, an immersion by plunging; also, a large bath
      in which the bather can wholly immerse himself.

   {Plunge}, or {plunging}, {battery} (Elec.), a voltaic battery
      so arranged that the plates can be plunged into, or
      withdrawn from, the exciting liquid at pleasure.

Plunge \Plunge\, n.
   1. The act of thrusting into or submerging; a dive, leap,
      rush, or pitch into, or as into, water; as, to take the
      water with a plunge.

   2. Hence, a desperate hazard or act; a state of being
      submerged or overwhelmed with difficulties. [R.]

            She was brought to that plunge, to conceal her
            husband's murder or accuse her son.   --Sir P.
                                                  Sidney.

            And with thou not reach out a friendly arm, To raise
            me from amidst this plunge of sorrows? --Addison.

   3. The act of pitching or throwing one's self headlong or
      violently forward, like an unruly horse.

   4. Heavy and reckless betting in horse racing; hazardous
      speculation. [Cant]

   {Plunge bath}, an immersion by plunging; also, a large bath
      in which the bather can wholly immerse himself.

   {Plunge}, or {plunging}, {battery} (Elec.), a voltaic battery
      so arranged that the plates can be plunged into, or
      withdrawn from, the exciting liquid at pleasure.

Source : WordNet®

plunge
     n 1: a brief swim in water [syn: {dip}]
     2: a steep and rapid fall

plunge
     v 1: thrust or throw into; "Immerse yourself in hot water" [syn:
          {immerse}]
     2: drop steeply; "the stock market plunged" [syn: {dive}, {plunk}]
     3: dash violently or with great speed or impetuosity; "She
        plunged at it eagerly"
     4: begin with vigor; "He launched into a long diatribe"; "She
        plunged into a dangerous adventure" [syn: {launch}]
     5: cause to be immersed; "The professor plunged his students
        into the study of the Italian text" [syn: {immerse}]
     6: fall abruptly; "It plunged to the bottom of the well" [syn:
        {dump}]
     7: immerse briefly into a liquid so as to wet, coat, or
        saturate; "dip the garment into the cleaning solution";
        "dip the brush into the paint" [syn: {dunk}, {dip}, {souse},
         {douse}]
     8: engross (oneself) fully; "He immersed himself into his
        studies" [syn: {steep}, {immerse}, {engulf}, {engross}, {absorb},
         {soak up}]