Source : Webster's Revised Unabridged Dictionary (1913)

T \T\ (t[=e]),
   the twentieth letter of the English alphabet, is a nonvocal
   consonant. With the letter h it forms the digraph th, which
   has two distinct sounds, as in thin, then. See Guide to
   Pronunciation, [sect][sect]262-264, and also [sect][sect]153,
   156, 169, 172, 176, 178-180. The letter derives its name and
   form from the Latin, the form of the Latin letter being
   further derived through the Greek from the Ph[oe]nician. The
   ultimate origin is probably Egyptian. It is etymologically
   most nearly related to d, s, th; as in tug, duke; two, dual,
   L. duo; resin, L. resina, Gr. "rhti`nh, tent, tense, a.,
   tenuous, thin; nostril, thrill. See {D}, {S}.

   {T bandage} (Surg.), a bandage shaped like the letter T, and
      used principally for application to the groin, or
      perineum.

   {T cart}, a kind of fashionable two seated wagon for pleasure
      driving.

   {T iron}.
   (a) A rod with a short crosspiece at the end, -- used as a
       hook.
   (b) Iron in bars, having a cross section formed like the
       letter T, -- used in structures.

   {T rail}, a kind of rail for railroad tracks, having no
      flange at the bottom so that a section resembles the
      letter T.

   {T square}, a ruler having a crosspiece or head at one end,
      for the purpose of making parallel lines; -- so called
      from its shape. It is laid on a drawing board and guided
      by the crosspiece, which is pressed against the straight
      edge of the board. Sometimes the head is arranged to be
      set at different angles.

   {To a T}, exactly, perfectly; as, to suit to a T. [Colloq.]

Source : WordNet®

T
     n 1: a base found in DNA (but not in RNA) and derived from
          pyrimidine; pairs with adenine [syn: {thymine}]
     2: one of the four nucleotides used in building DNA; all four
        nucleotides have a common phosphate group and a sugar
        (ribose) [syn: {deoxythymidine monophosphate}]
     3: a unit of weight equivalent to 1000 kilograms [syn: {metric
        ton}, {MT}, {tonne}]
     4: a unit of information equal to a trillion
        (1,099,511,627,776) bytes or 1024 gigabytes [syn: {terabyte},
         {TB}]
     5: the 20th letter of the Roman alphabet
     6: thyroid hormone similar to thyroxine but with one less
        iodine atom per molecule and produced in smaller quantity;
        exerts the same biological effects as thyroxine but is
        more potent and briefer [syn: {triiodothyronine}, {liothyronine}]
     7: hormone produced by the thyroid glands to regulate
        metabolism by controlling the rate of oxidation in cells;
        "thyroxine is 65% iodine" [syn: {thyroxine}, {thyroxin}, {tetraiodothyronine}]

Source : Free On-Line Dictionary of Computing

\t
     
        {horizontal tabulation}

T
     
        1. True.  A {Lisp} compiler by Johnathan A. Rees in 1982 at
        {Yale University}.  T has {static scope} and is a
        near-superset of {Scheme}.  {Unix} source is available.  T is
        written in itself and compiles to efficient native code.  Used
        as the basis for the Yale {Haskell} system.  Maintained by
        David Kranz .
     
        Current version: 3.1.
     
        {(ftp://ftp.ai.mit.edu/pub/systems/t3.1)}.
     
        A {multiprocessing} version of T is available
        {(ftp://masala.lcs.mit.edu/pub/mult)}.
     
        Runs on {Decstation}, {SPARC}, {Sun-3}, {Vax} under {Unix},
        {Encore}, {HP}, {Apollo}, {Macintosh} under {A/UX}.
     
        E-mail:  (bugs).
        E-mail: .
     
        (1991-11-26)
     
        ["The T Manual", Johnathan A. Rees  et
        al, Yale U, 1984].
     
        2. A {functional language}.
     
        ["T: A Simple Reduction Language Based on Combinatory Term
        Rewriting", Ida et al, Proc of Prog Future Generation
        Computers, 1988].
     
        3. (lower case) The {Lisp} {atom} used to represent "true",
        among other things.  "false" is represented using the same
        atom as an empty list, {nil}.  This {overloading} of the basic
        constants of the language helps to make Lisp {write-only
        code}.
     
        4. In transaction-processing circles, an abbreviation for
        "transaction".
     
        5. (Purdue) An alternative spelling of "{tee}".