The Collaborative International Dictionary of English v.0.48:

Manager \Man"a*ger\, n.
   1. One who manages; a conductor or director; as, the manager
      of a theater.
      [1913 Webster]

            A skillful manager of the rabble.     --South.
      [1913 Webster]

   2. A person who conducts business or household affairs with
      economy and frugality; a good economist.
      [1913 Webster]

            A prince of great aspiring thoughts; in the main, a
            manager of his treasure.              --Sir W.
                                                  Temple.
      [1913 Webster]

   3. A contriver; an intriguer. --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

manager
    n 1: someone who controls resources and expenditures [syn:
         director, manager, managing director]
    2: (sports) someone in charge of training an athlete or a team
       [syn: coach, manager, handler]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "manager":
   administrator, agent, banker, baron, big boss, big businessman,
   boss, business leader, businessman, captain, captain of industry,
   castellan, chatelain, chatelaine, chief, commandant, commander,
   conductor, deputy, directeur, director, enterpriser, entrepreneur,
   exec, executive, financier, foreman, governor, handler, head,
   impresario, industrialist, intendant, king, little businessman,
   magnate, man of commerce, master, officer, official, overseer,
   producer, proprietor, rector, responsible person, ruler,
   straw boss, supercargo, superintendent, supervisor, top executive,
   tycoon



Bouvier's Law Dictionary, Revised 6th Ed (1856):

MANAGER. A person, appointed or elected to manage the affairs of another,
but the term is more usually applied to those officers of a corporation who
are authorized to manage its affairs. 1 Bouv. Inst. n. 190.
     2. In banking corporations these officers are commonly called
directors, and the power to conduct the affairs of the company, is vested in
a board of directors. In other private corporations, such as railroad
companies, canal, coal companies, and the like, these officers are called
managers. Being agents, when their authority is limited, they have no power
to bind their principal beyond such authority. 17 Mass. R. 29; 1 Greenl. R.
81.
     3. The persons appointed on the part of the house of representatives to
prosecute impeachments before the senate, are called managers.