From Longman Dictionary of Contemporary Englishcontrol keyconˈtrol ˌkey noun [countable] TDa particular button on a computer that allows you to do certain operations
Examples from the Corpus
control key• Flame control: the control key allows quite fine flame adjustment, though you need practice to get this right.• If the control key is left attached to the adjustment spindle it rapidly becomes too hot for comfortable handling.From Longman Business Dictionarycontrol keyconˈtrol key written abbreviation ctl-keyCOMPUTING a key that is used together with other keys to give commands, obtain special characters etcThe control key must be held down while the R or W key on the keyboard is pressed. → key 