The Collaborative International Dictionary of English v.0.48:

Idyl \I"dyl\, n. [L. idyllium, Gr. ?, fr. ? form; literally, a
   little form of image: cf. F. idylle. See Idol.]
   A short poem; properly, a short pastoral poem; as, the idyls
   of Theocritus; also, any poem, especially a narrative or
   descriptive poem, written in an eleveted and highly finished
   style; also, by extension, any artless and easily flowing
   description, either in poetry or prose, of simple, rustic
   life, of pastoral scenes, and the like. [Written also
   idyll.]
   [1913 Webster]

         Wordsworth's solemn-thoughted idyl.      --Mrs.
                                                  Browning.
   [1913 Webster]

         His [Goldsmith's] lovely idyl of the Vicar's home. --F.
                                                  Harrison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

idyll
    n 1: an episode of such pastoral or romantic charm as to qualify
         as the subject of a poetic idyll
    2: a musical composition that evokes rural life [syn:
       pastorale, pastoral, idyll, idyl]
    3: a short poem descriptive of rural or pastoral life [syn:
       eclogue, bucolic, idyll, idyl]