The Collaborative International Dictionary of English v.0.48:

Mentor \Men"tor\, n. [From Mentor, the counselor of Telemachus,
   Gr. Me`ntwr, prop., counselor. Cf. Monitor.]
   A wise and faithful counselor or monitor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mentor
    n 1: a wise and trusted guide and advisor [syn: mentor, wise
         man]
    v 1: serve as a teacher or trusted counselor; "The famous
         professor mentored him during his years in graduate
         school"; "She is a fine lecturer but she doesn't like
         mentoring"

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "mentor":
   Dutch uncle, Polonius, abecedarian, admonisher, adviser, authority,
   backseat driver, buttinsky, certified teacher, coach, confidant,
   consultant, counsel, counselor, docent, doctor, dominie, don,
   educationist, educator, elder, elder statesman, expert, fellow,
   forerunner, great soul, guide, guru, illuminate, instructor,
   intellect, intellectual, kibitzer, lover of wisdom, maestro,
   mahatma, man of intellect, man of wisdom, mandarin, master,
   mastermind, meddler, melamed, monitor, mullah, nestor, oracle,
   orienter, pandit, pathfinder, pedagogist, pedagogue, philosopher,
   preceptist, preceptor, preparationist, preparator, preparer,
   professor, pundit, rabbi, rishi, sage, sapient, savant, scholar,
   schoolkeeper, schoolmaster, schoolteacher, seer, starets, teacher,
   thinker, trailblazer, trainer, wise man, wise old man



The Free On-line Dictionary of Computing (30 December 2018):

MENTOR

   CAI language.  "Computer Systems for Teaching Complex
   Concepts", Report 1742, BBN, Mar 1969.


U.S. Gazetteer Places (2000):

Mentor, OH -- U.S. city in Ohio
   Population (2000):    50278
   Housing Units (2000): 19301
   Land area (2000):     26.768950 sq. miles (69.331260 sq. km)
   Water area (2000):    1.306725 sq. miles (3.384402 sq. km)
   Total area (2000):    28.075675 sq. miles (72.715662 sq. km)
   FIPS code:            49056
   Located within:       Ohio (OH), FIPS 39
   Location:             41.691245 N, 81.341955 W
   ZIP Codes (1990):     44060
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Mentor, OH
    Mentor


U.S. Gazetteer Places (2000):

Mentor, KY -- U.S. city in Kentucky
   Population (2000):    181
   Housing Units (2000): 73
   Land area (2000):     0.536004 sq. miles (1.388243 sq. km)
   Water area (2000):    0.038721 sq. miles (0.100287 sq. km)
   Total area (2000):    0.574725 sq. miles (1.488530 sq. km)
   FIPS code:            51564
   Located within:       Kentucky (KY), FIPS 21
   Location:             38.890716 N, 84.245637 W
   ZIP Codes (1990):
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Mentor, KY
    Mentor


U.S. Gazetteer Places (2000):

Mentor, MN -- U.S. city in Minnesota
   Population (2000):    150
   Housing Units (2000): 102
   Land area (2000):     1.891360 sq. miles (4.898600 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    1.891360 sq. miles (4.898600 sq. km)
   FIPS code:            41714
   Located within:       Minnesota (MN), FIPS 27
   Location:             47.699006 N, 96.142096 W
   ZIP Codes (1990):     56736
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Mentor, MN
    Mentor