1 head, leader, principal, superior, supervisor, superintendent, manager, overseer, captain, master, ringleader, chieftain, Dialect himself, Colloq boss, bossman, Brit governor, gov., supremo, US man, kingpin, (head or chief) honcho, number one, numero uno, headman, big White Chief, big Chief, Great White Father, big Daddy, super; Slang big cheese, Brit gaffer, Chiefly US Mr Big:
You'd best ask the chief for permission to fly to Rome.
2 head, leading, ranking, superior, supreme, foremost, premier, first, greatest, outstanding:
Terry is your chief competition for the singles trophy.
3 principal, most important, essential, key, paramount, (first and) foremost, primary, prime, main:
The chief reason I came was to see you. Here is a list of the chief crimes committed in the area last year.