NOUN (2)

1. spiritual leader of a Jewish congregation; qualified to expound and apply Jewish law;

2. a Hebrew title of respect for a Jewish scholar or teacher;

The Collaborative International Dictionary of English v.0.48:

Rabbi \Rab"bi\ (r[a^]r"b[imac] or r[a^]r"b[i^]; 277), n.; pl.
   Rabbis (r[a^]r"b[imac]z or r[a^]r"b[i^]z) or Rabbies.
   [L., fr. Gr. "rabbi`, Heb. rab[imac] my master, from rab
   master, lord, teacher, akin to Ar. rabb.]
   Master; lord; teacher; -- a Jewish title of respect or honor
   for a teacher or doctor of the law. "The gravest rabbies."
   --Milton.
   [1913 Webster]

         Be not ye called Rabbi, for one is your Master, even
         Christ, and all ye are brethren.         --Matt. xxiii.
                                                  8.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rabbi
    n 1: spiritual leader of a Jewish congregation; qualified to
         expound and apply Jewish law
    2: a Hebrew title of respect for a Jewish scholar or teacher

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "rabbi":
   Levite, abecedarian, authority, baal kore, boss, bwana, cantor,
   certified teacher, chef, chief, chief rabbi, church dignitary,
   docent, doctor, dominie, don, ecclesiarch, educationist, educator,
   elder, elder statesman, employer, fellow, goodman, great soul,
   guide, guru, high priest, husband, illuminate, instructor,
   intellect, intellectual, kohen, liege, liege lord, lord,
   lord paramount, lover of wisdom, maestro, mahatma,
   man of intellect, man of wisdom, mandarin, master, mastermind,
   melamed, mentor, mullah, oracle, overlord, padrone, pandit,
   paramount, paterfamilias, patriarch, patron, pedagogist, pedagogue,
   philosopher, preceptor, priest, professor, pundit, rabbin, rishi,
   sage, sahib, sapient, savant, scholar, schoolkeeper, schoolmaster,
   schoolteacher, scribe, seer, seigneur, seignior, starets, teacher,
   thinker, wise man, wise old man



Easton's 1897 Bible Dictionary:

Rabbi
   my master, a title of dignity given by the Jews to their doctors
   of the law and their distinguished teachers. It is sometimes
   applied to Christ (Matt. 23:7, 8; Mark 9:5 (R.V.); John 1:38,
   49; 3:2; 6:25, etc.); also to John (3:26).


Hitchcock's Bible Names Dictionary (late 1800's):

Rabbi, Rabboni, my master