From WordNet (r) 2.0 (August 2003) [wn]:
episode
n 1: a happening that is distinctive in a series of related
events
2: a brief section of a literary or dramatic work that forms
part of a connected series
3: a part of a broadcast serial [syn: installment,
instalment]
4: film consisting of a succession of related shots that
develop a given subject in a movie [syn: sequence]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Episode \Ep"i*sode\, n. [Gr. ? a coming in besides, ? episode; ?
into, besides + ? a coming in, ? into + ? way, cf. Skr. sad
to go: cf. F. ['e]pisode.] (Rhet.)
A separate incident, story, or action, introduced for the
purpose of giving a greater variety to the events related; an
incidental narrative, or digression, separable from the main
subject, but naturally arising from it.
[1913 Webster]