Definition of chief :
1. Highest in office or rank; principal; head.
2. Principal or most eminent in any quality or action; most distinguished; having most influence; taking the lead; most important; as, the chief topic of conversation; the chief interest of man.
3. The head or leader of any body of men; a commander, as of an army; a head man, as of a tribe, clan, or family; a person in authority who directs the work of others; the principal actor or agent.
4. The principal part; the most valuable portion.
5. The upper third part of the field. It is supposed to be composed of the dexter, sinister, and middle chiefs.
6. Very intimate, near, or close.
hirer, capitulum, taskmistress, forefront, headsman, heading, nous, main, antique, tribal chief, knob, over, important, promontory, headway, pass, mind, point, headland, honcho, psyche, headman, header, old-timer, party boss, straw boss, head word, hierarch, of import, forewoman, chieftain, question, old geezer, top, top dog, read/write head, foreperson, drumhead, political boss, brain, straits, caput, head teacher, gaffer, primary, oldtimer, fountainhead, school principal, headspring, study at principal, oral sex, foreland, arch
director (part of speech: noun)
superior (part of speech: noun)
choice, most, chosen, above, ruling, sovereign, A-1, leading, foremost, senior, superman, superior, champion, king, dominant, paragon, aristocracy, prize winner, maximum, superwoman, prodigy, prima donna, elite, zenith, headmost, supreme, champ, paramount, signal, predominant, eminent, best, controlling, exceller, nobility, wonderwoman, premier, winner, commanding, better, crowning, consummate, ascendant, virtuoso, victor, quintessential, master, furthermost, furthest, uppermost
master (part of speech: noun)
manager, officer, abbot, president, maestro, squire, headmistress, head, commandant, landlady, mandarin, kingpin, leader, Lord, ruler, proprietress, landlord, executive, titleholder, star, headmaster, authority, sire, captain, dean, commander, quartermaster, mahatma, proprietor, guru, governor, mother, director, principal