The Collaborative International Dictionary of English v.0.48:

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.
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            Bound and plunged him into a cell.    --Tennyson.
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            We shall be plunged into perpetual errors. --I.
                                                  Watts.
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   2. To baptize by immersion.
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   3. To entangle; to embarrass; to overcome. [Obs.]
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            Plunged and graveled with three lines of Seneca.
                                                  --Sir T.
                                                  Browne.
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