Definition of leader 1. Something or someone that shows the way: conductor, director, escort, guide, lead, pilot, shepherd, usher. See show/hide. 2. A leading contestant: front-runner, number one. See precede/follow. 3. One who is highest in rank or authority: boss, chief, chieftain, director, head, headman, hierarch, master. Slang honcho. Idioms: cock of the walk. See over/under. 4. A professional politician who controls a party or political machine: boss, chief. See over/under. 5. An important, influential person: character, dignitary, eminence, lion, nabob, notability, notable, personage. Informal big-timer, heavyweight, somebody, someone, VIP. Slang big shot, big wheel, bigwig, muckamuck. See important/unimportant. 6. A prominent article in a periodical: feature, lead. See words.