The Collaborative International Dictionary of English v.0.48:

Tee \Tee\, n.
   1. A short piece of pipe having a lateral outlet, used to
      connect a line of pipe with a pipe at a right angle with
      the line; -- so called because it resembles the letter T
      in shape.
      [1913 Webster]

   2. The letter T, t; also, something shaped like, or
      resembling in form, the letter T.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Tee \Tee\, v. t. [imp. & p. p. Teed; p. pr. & vb. n.
   Teeing.] (Golf)
   To place (the ball) on a tee; also called to tee up.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Tee \Tee\, n. [Cf. Icel. tj[=a] to show, mark.]
   (a) The mark aimed at in curling and in quoits.
   (b) The nodule of earth, or a short peg stuck into the
       ground, from which the ball is struck at the beginning of
       play for each hole in golf.
       [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

tee
    n 1: the starting place for each hole on a golf course; "they
         were waiting on the first tee" [syn: tee, teeing
         ground]
    2: support holding a football on end and above the ground
       preparatory to the kickoff [syn: tee, football tee]
    3: a short peg put into the ground to hold a golf ball off the
       ground [syn: tee, golf tee]
    v 1: place on a tee; "tee golf balls" [syn: tee, tee up]
    2: connect with a tee; "tee two pipes"

The Jargon File (version 4.4.7, 29 Dec 2003):

tee
 n.,vt.

    [Purdue] A carbon copy of an electronic transmission. ?Oh, you're sending
    him the bits to that? Slap on a tee for me.? From the Unix command tee(1)
    , itself named after a pipe fitting (see plumbing). Can also mean ?save
    one for me?, as in ?Tee a slice for me!? Also spelled ?T?.


The Free On-line Dictionary of Computing (30 December 2018):

tee

    A Unix command which copies its
   standard input to its standard output (like cat) but
   also to a file given as its argument.  tee is thus useful in
   pipelines of Unix commands (see plumbing) where it
   allows you to create a duplicate copy of the data stream.
   E.g.

   	egrep Unix Dictionary | tee /dev/tty | wc -l

   searches for lines containing the string "Unix" in the file
   "Dictionary", prints them to the terminal (/dev/tty) and
   counts them.

   Unix manual page: tee(1).

   [Jargon File]

   (1996-01-22)