1. [n]  sour-tasting liquid produced usually by oxidation of the alcohol in wine or cider and used as a condiment or food preservative
2. [n]  dilute acetic acid

Vinegar
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1. \Vin"e*gar\, n. [OE. vinegre, F. vinaigre; vin wine (L.
   vinum) + aigre sour. See {Wine}, and {Eager}, a.]
   1. A sour liquid used as a condiment, or as a preservative,
      and obtained by the spontaneous (acetous) fermentation, or
      by the artificial oxidation, of wine, cider, beer, or the
      like.
   Note: The characteristic sourness of vinegar is due to acetic
         acid, of which it contains from three to five per cent.
         Wine vinegar contains also tartaric acid, citric acid,
         etc.
   2. Hence, anything sour; -- used also metaphorically.
            Here's the challenge: . . . I warrant there's
            vinegar and pepper in't.              --Shak.
   {Aromatic vinegar}, strong acetic acid highly flavored with
      aromatic substances.
   {Mother of vinegar}. See 4th {Mother}.
   {Radical vinegar}, acetic acid.
   {Thieves' vinegar}. See under {Thief}.
   {Vinegar eel} (Zo["o]l.), a minute nematode worm ({Leptodera
      oxophila}, or {Anguillula acetiglutinis}), commonly found
      in great numbers in vinegar, sour paste, and other
      fermenting vegetable substances; -- called also {vinegar
      worm}.
   {Vinegar lamp} (Chem.), a fanciful name of an apparatus
      designed to oxidize alcohol to acetic acid by means of
      platinum.
   {Vinegar plant}. See 4th {Mother}.
   {Vinegar tree} (Bot.), the stag-horn sumac ({Rhus typhina}),
      whose acid berries have been used to intensify the
      sourness of vinegar.
   {Wood vinegar}. See under {Wood}.
   

2. \Vin"e*gar\, v. t.
   To convert into vinegar; to make like vinegar; to render sour
   or sharp. [Obs.]
         Hoping that he hath vinegared his senses As he was bid.
                                                  --B. Jonson.
   

Heb. hometz, Gr. oxos, Fr. vin aigre; i.e., "sour wine." The Hebrew word is rendered vinegar in Ps. 69:21, a prophecy fulfilled in the history of the crucifixion (Matt. 27:34). This was the common sour wine (posea) daily made use of by the Roman soldiers. They gave it to Christ, not in derision, but from compassion, to assuage his thirst. Prov. 10:26 shows that there was also a stronger vinegar, which was not fit for drinking. The comparison, "vinegar upon nitre," probably means "vinegar upon soda" (as in the marg. of the R.V.), which then effervesces.