The Collaborative International Dictionary of English v.0.48:

caesar \c[ae]"sar\ (s[=e]"z[~e]r), n. [L.]
   A Roman emperor, as being the successor of Augustus C[ae]sar.
   Hence, a kaiser, or emperor of Germany, or any emperor or
   powerful ruler. See Kaiser, Kesar, Tsar.
   [1913 Webster]

         Marlborough anticipated the day when he would be
         servilely flattered and courted by C[ae]sar on one side
         and by Louis the Great on the other.     --Macaulay.
   [1913 Webster] C[ae]sarean

WordNet (r) 3.0 (2006):

Caesar
    n 1: conqueror of Gaul and master of Italy (100-44 BC) [syn:
         Caesar, Julius Caesar, Gaius Julius Caesar]
    2: United States comedian who pioneered comedy television shows
       (born 1922) [syn: Caesar, Sid Caesar, Sidney Caesar]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "caesar":
   Dalai Lama, Holy Roman Emperor, Inca, Kaiser, Simon Legree,
   absolute monarch, absolute ruler, all-powerful ruler, ardri,
   arrogator, autarch, autocrat, bey, cacique, cham, commissar, czar,
   despot, dictator, disciplinarian, driver, duce, hard master, kaid,
   khan, martinet, mikado, negus, oligarch, oppressor, padishah,
   pendragon, pharaoh, rig, sachem, sagamore, shah, sheikh, shogun,
   slave driver, stickler, tenno, tycoon, tyrant, usurper, warlord



Easton's 1897 Bible Dictionary:

Caesar
   the title assumed by the Roman emperors after Julius Caesar. In
   the New Testament this title is given to various emperors as
   sovereigns of Judaea without their accompanying distinctive
   proper names (John 19:15; Acts 17:7). The Jews paid tribute to
   Caesar (Matt. 22:17), and all Roman citizens had the right of
   appeal to him (Acts 25:11). The Caesars referred to in the New
   Testament are Augustus (Luke 2:1), Tiberius (3:1; 20:22),
   Claudius (Acts 11:28), and Nero (Acts 25:8; Phil. 4:22).