The Collaborative International Dictionary of English v.0.48:

Apothegm \Ap"o*thegm\, Apophthegm \Ap"oph*thegm\, n. [Gr.
   'apo`fqegma thing uttered, apothegm, from 'apofqe`ggesqai to
   speak out; 'apo` from + fqe`ggesqai to speak.]
   A short, pithy, and instructive saying; a terse remark,
   conveying some important truth; a sententious precept or
   maxim.

   Note: [Apothegm is now the prevalent spelling in the United
         States.]
         [1913 Webster] Apothegmatic

WordNet (r) 3.0 (2006):

apothegm
    n 1: a short pithy instructive saying [syn: aphorism,
         apothegm, apophthegm]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "apothegm":
   adage, ana, analects, aphorism, axiom, bon mot, boutade,
   bright idea, bright thought, brilliant idea, brocard, byword,
   catchword, collected sayings, conceit, crack, current saying,
   dictate, dictum, distich, epigram, expression, facetiae,
   flash of wit, flight of wit, gibe, gnome, golden saying,
   happy thought, maxim, moral, mot, motto, nasty crack, oracle,
   persiflage, phrase, pithy saying, play of wit, pleasantry, precept,
   prescript, proverb, proverbial saying, proverbs, quip,
   quips and cranks, repartee, retort, riposte, rule, sally, saw,
   saying, scintillation, sentence, sententious expression, sloka,
   smart crack, smart saying, snappy comeback, stock saying,
   stroke of wit, sutra, teaching, text, truism, turn of thought,
   verse, wisdom, wisdom literature, wise saying, wisecrack,
   witticism, word, words of wisdom