1. (a.) Acting; -- opposed to patient, or sustaining, action.

2. (n.) One who exerts power, or has the power to act; an actor.

3. (n.) One who acts for, or in the place of, another, by authority from him; one entrusted with the business of another; a substitute; a deputy; a factor.

4. (n.) An active power or cause; that which has the power to produce an effect; as, a physical, chemical, or medicinal agent; as, heat is a powerful agent.

Charlie McCarthy Federal acid acidity acolyte activator actor adjutant administrator advocate agency aid aide aide-de-camp aider alkali alkalinity alloisomer amanuensis amicus curiae ancilla anion antacid appliance appointee architect assignee assistant atom attendant attorney attorney-at-law author auxiliary baggage agent barrister barrister-at-law base begetter beginner best man biochemical broker business agent buyer candidate catalyst cation cause causer channel chemical chemical element chromoisomer claim agent clerk coadjutant coadjutor coadjutress coadjutrix commercial agent commission agent commissionaire commissioner compound conductor connection consignee contrivance copolymer counsel counselor counselor-at-law creator creature customer agent delegate deputy device dimer directeur director distributor doer driver dummy dupe effector element emissary energizer engenderer engineer envoy executant executive executive officer executor executrix fabricator factor father fed federal agent force freight agent friend at court front front man functionary general agent generator go-between governor handler handmaid handmaiden heavy chemicals help helper helpmate helpmeet high polymer homopolymer hydracid implement impresario ingredient inorganic chemical inspirer instigator instrument instrumentality instrumentation insurance agent intendant interagent interceder intercessor intermediary intermediate intermediate agent intermediator intermedium internuncio intervener interventionist interventor ion isomer jobber land agent law agent lawyer legal adviser legal counselor legal expert legal practitioner legalist legate lever liaison licensee lieutenant link literary agent loan agent macromolecule maker manager manipulator means mechanism mediary mediator medium metamer middleman midwife minion minister ministry molecule monomer mother mouthpiece mover negotiant negotiator negotiatress negotiatrix neutralizer news agent nominee nonacid official ombudsman operant operative operator organ organic chemical originator oxyacid paranymph paraprofessional parent parliamentary agent passenger agent pawn performer perpetrator pilot plaything pleader polymer power practitioner press agent prime mover primum mobile proctor procurator producer proxy pseudoisomer puppet purchasing agent radical reagent real estate agent rector representative responsible person runner sales agent sea lawyer second secretary selectee self-styled lawyer servant sideman sire slave solicitor special agent spokesman spokesperson spokeswoman spook spy station agent steersman