leader

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that leads or guides.
• noun One who is in charge or in command of others.
• noun One who heads a political party or organization.
• noun One who has influence or power, especially of a political nature.
• noun A conductor, especially of an orchestra, band, or choral group.
• noun The principal performer in an orchestral section or a group.
• noun The foremost animal, such as a horse or dog, in a harnessed team.
• noun A loss leader.
• noun Chiefly British The main editorial in a newspaper.
• noun Printing Dots or dashes in a row leading the eye across a page, as in an index entry.
• noun A pipe for conducting liquid.
• noun A short length of fishing line between the main line and the hook.
• noun A blank strip at the end or beginning of a film or tape used in threading or winding.
• noun Botany The growing apex or main shoot of a shrub or tree.
• noun An economic indicator.

from The Century Dictionary.

• noun A plumber.
• noun The first player on any trick in a game of cards; the player who sits on the dealer's left.
• noun One who leads, guides, conducts, directs, or controls; a director or conductor; a chief or commander.
• noun One who is first or most prominent in any relation; one who takes precedence by virtue of superior qualification or influence; a recognized principal or superior: as, leaders of society; a leader of the bar.
• noun In the Meth. Epis. Ch., one who has charge of a “class,” which he meets at stated times, and over which he exercises a quasi-pastoral supervision. See class, n., 3 .
• noun In music:
• noun A conductor or director.
• noun The principal first-violin player in an orchestra (concert-master), the principal cornettist in a band, or the principal soprano in a chorus.
• noun That which leads or conducts; something that guides the course of a thing, or conducts to it.
• noun In surveying, the foremost of the two chain-carriers.
• noun A ring or gripper used for leading cattle, passed through the septum of the nose.
• noun That which precedes; something that has a leading or foremost place, whether in actual position or in importance.
• noun The principal wheel in a set of machinery.
• noun A principal editorial article in a newspaper; one of the longer articles in a newspaper appearing as its own utterances or expressions of editorial views, whether written by the ostensible editor or by leader-writers or contributors.
• noun A sinew; a tendon: as, the leaders of the fingers or toes.
• noun Something offered as a special attraction to customers; a leading “bargain.”
• noun In botany, the terminal shoot of an excurrent trunk, commonly forming the apex of a cone-shaped tree, as in the fir and the larch.
• noun = Syn. 1 and 2. Commander, Head, etc. See chief.

from the GNU version of the Collaborative International Dictionary of English.

• noun Obs. or R., Obs. or R. One who, or that which, leads or conducts; a guide; a conductor.
• noun Obs. or R., Obs. or R. One who goes first.
• noun Obs. or R., Obs. or R. One having authority to direct; a chief; a commander.
• noun (Mus.), Obs. or R., Obs. or R. A performer who leads a band or choir in music; also, in an orchestra, the principal violinist; the one who plays at the head of the first violins.
• noun (Naut.), Obs. or R., Obs. or R. A block of hard wood pierced with suitable holes for leading ropes in their proper places.
• noun (Mach.), Obs. or R. The principal wheel in any kind of machinery.
• noun A horse placed in advance of others; one of the forward pair of horses.
• noun A pipe for conducting rain water from a roof to a cistern or to the ground; a conductor.
• noun (Fishing) A net for leading fish into a pound, weir, etc.; also, a line of gut, to which the snell of a fly hook is attached.
• noun (Mining) A branch or small vein, not important in itself, but indicating the proximity of a better one.
• noun The first, or the principal, editorial article in a newspaper; a leading or main editorial article.
• noun A type having a dot or short row of dots upon its face.
• noun a row of dots, periods, or hyphens, used in tables of contents, etc., to lead the eye across a space to the right word or number.