Merriam-Webster Collegiate Dictionary - activate

 verb  (-vated; -vating)  Date: 1626  transitive verb to make active or more active: as  a.  (1) to make (as molecules) reactive or more reactive  (2) to convert (as a provitamin) into a biologically active derivative  b. to make (a substance) radioactive  c. to treat (as carbon or alumina) so as to improve adsorptive properties  d.  (1) to set up or formally institute (as a military unit) with the necessary personnel and equipment  (2) to put (an individual or unit) on active duty  intransitive verb to become active  • activation noun  • activator noun