activator /ak″tivā′tər/ , 1. a substance, force, or device that stimulates activity in another substance or structure, especially a substance that activates an enzyme. 2. a substance that stimulates the development of an anatomical structure in the embryo. 3. an internal secretion of the pancreas. 4. an apparatus for making substances radioactive, such as a cyclotron or neutron generator. 5. (in dentistry) a removable orthodontic appliance that functions as a passive transmitter and stimulator of the perioral muscles.
