'Trilogy' definitions:

Definition of 'trilogy'

(from WordNet)
noun
A set of three literary or dramatic works related in subject or theme

Definition of 'Trilogy'

From: GCIDE
  • Trilogy \Tril"o*gy\, n. [Gr. trilogi`a; pref. tri- (see Tri-) + lo`gos speech, discourse: cf. F. trilogie.] A series of three dramas which, although each of them is in one sense complete, have a close mutual relation, and form one historical and poetical picture. Shakespeare's " Henry VI." is an example. [1913 Webster]
  • On the Greek stage, a drama, or acted story, consisted in reality of three dramas, called together a trilogy, and performed consecutively in the course of one day. --Coleridge. [1913 Webster] Triluminar