The Collaborative International Dictionary of English v.0.48:

Control \Con*trol"\, n. [F. contr[^o]le a counter register,
   contr. fr. contr-r[^o]le; contre (L. contra) + r[^o]le roll,
   catalogue. See Counter and Roll, and cf. Counterroll.]
   1. A duplicate book, register, or account, kept to correct or
      check another account or register; a counter register.
      [Obs.] --Johnson.
      [1913 Webster]

   2. That which serves to check, restrain, or hinder;
      restraint. "Speak without control." --Dryden.
      [1913 Webster]

   3. Power or authority to check or restrain; restraining or
      regulating influence; superintendence; government; as,
      children should be under parental control.
      [1913 Webster]

            The House of Commons should exercise a control over
            all the departments of the executive administration.
                                                  --Macaulay.
      [1913 Webster]

   4. (Mach.) The complete apparatus used to control a mechanism
      or machine in operation, as a flying machine in flight;
      specifically (A["e]ronautics), the mechanism controlling
      the rudders and ailerons.
      [Webster 1913 Suppl.]

   5. (Climatology) Any of the physical factors determining the
      climate of any particular place, as latitude,distribution
      of land and water, altitude, exposure, prevailing winds,
      permanent high- or low-barometric-pressure areas, ocean
      currents, mountain barriers, soil, and vegetation.
      [Webster 1913 Suppl.]

   6. (Technology) in research, an object or subject used in an
      experimental procedure, which is treated identically to
      the primary subject of the experiment, except for the
      omission of the specific treatment or conditions whose
      effect is being investigated. If the control is a group of
      living organisms, as is common in medical research, it is
      called the

   control group.

   Note: For most experimental procedures, the results are not
         considered valid and reliable unless a proper control
         experiment is performed. There are various types of
         control used in experimental science, and often several
         groups of subjects serve as controls, being subjected
         to different variations of the experimental procedure,
         or controlling for several variables being tested. When
         the effects caused by an experimental treatment are not
         consistent and obvious, statistical analysis of the
         results is typically used to determine if there are any
         significant differences between the effects of
         different experimental conditions.
         [PJC]

   7. (Technology) the part of an experimental procedure in
      which the controls[6] are subjected to the experimental
      conditions.
      [PJC]

   8. the group of technical specialists exercising control by
      remote communications over a distant operation, such as a
      space flight; as, the American Mission Control for manned
      flights is located in Houston.
      [PJC]

   Board of control. See under Board.
      [1913 Webster]