The Collaborative International Dictionary of English v.0.48:

Chair \Chair\, v. t. [imp. & p. p. Chaired; p. pr. & vb. n.
   Chairing.]
   1. To place in a chair.
      [1913 Webster]

   2. To carry publicly in a chair in triumph. [Eng.]
      [1913 Webster]

   3. To function as chairperson of (a meeting, committee,
      etc.); as, he chaired the meeting.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Chair \Chair\ (ch[^a]r), n. [OE. chaiere, chaere, OF. chaiere,
   chaere, F. chaire pulpit, fr. L. cathedra chair, armchair, a
   teacher's or professor's chair, Gr. ? down + ? seat, ? to
   sit, akin to E. sit. See Sit, and cf. Cathedral,
   chaise.]
   [1913 Webster]
   1. A movable single seat with a back.
      [1913 Webster]

   2. An official seat, as of a chief magistrate or a judge, but
      esp. that of a professor; hence, the office itself.
      [1913 Webster]

            The chair of a philosophical school.  --Whewell.
      [1913 Webster]

            A chair of philology.                 --M. Arnold.
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   3. The presiding officer of an assembly; a chairman; as, to
      address the chair.
      [1913 Webster]

   4. A vehicle for one person; either a sedan borne upon poles,
      or two-wheeled carriage, drawn by one horse; a gig.
      --Shak.
      [1913 Webster]

            Think what an equipage thou hast in air,
            And view with scorn two pages and a chair. --Pope.
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   5. An iron block used on railways to support the rails and
      secure them to the sleepers.
      [1913 Webster]

   Chair days, days of repose and age.

   To put into the chair, to elect as president, or as
      chairman of a meeting. --Macaulay.

   To take the chair, to assume the position of president, or
      of chairman of a meeting.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chair
    n 1: a seat for one person, with a support for the back; "he put
         his coat over the back of the chair and sat down"
    2: the position of professor; "he was awarded an endowed chair
       in economics" [syn: professorship, chair]
    3: the officer who presides at the meetings of an organization;
       "address your remarks to the chairperson" [syn: president,
       chairman, chairwoman, chair, chairperson]
    4: an instrument of execution by electrocution; resembles an
       ordinary seat for one person; "the murderer was sentenced to
       die in the chair" [syn: electric chair, chair, death
       chair, hot seat]
    5: a particular seat in an orchestra; "he is second chair
       violin"
    v 1: act or preside as chair, as of an academic department in a
         university; "She chaired the department for many years"
         [syn: chair, chairman]
    2: preside over; "John moderated the discussion" [syn:
       moderate, chair, lead]