In experimentation, 'control' can be used as a noun meaning either the group which is not manipulated by the experimenter, or a measure taken to prevent confounds (or counfounding variables) from influencing the results. Example: "The experimental group took the drug we're testing, while the control group was treated exactly the same way, except that the pill they were given contained no active ingredient."

Also a verb meaning to take such measures. Example: "We thought that age of the subjects might introduce a confound, so we controlled for that by selecting only subjects born in May of 1944."