Source : Webster's Revised Unabridged Dictionary (1913)

Trilemma \Tri*lem"ma\, n. [NL., fr. Gr. ? (see {Tri-}) + {?} any
   thing received, in logic, an assumption. Cf. {Dilemma}.]
   1. (Logic) A syllogism with three conditional propositions,
      the major premises of which are disjunctively affirmed in
      the minor. See {Dilemma}.

   2. A state of things in which it is difficult to determine
      which one of three courses to pursue.