The Collaborative International Dictionary of English v.0.48:

Excursion \Ex*cur"sion\ [L. excursio: cf. F. excursion. See
   Excurrent.]
   1. A running or going out or forth; an expedition; a sally.
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            Far on excursion toward the gates of hell. --Milton.
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            They would make excursions and waste the country.
                                                  --Holland.
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   2. A journey chiefly for recreation; a pleasure trip; a brief
      tour; as, an excursion into the country.
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   3. A wandering from a subject; digression.
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            I am not in a scribbling mood, and shall therefore
            make no excursions.                   --Cowper.
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   4. (Mach.) Length of stroke, as of a piston; stroke. [An
      awkward use of the word.]

   Syn: Journey; tour; ramble; jaunt. See Journey.
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WordNet (r) 3.0 (2006):

excursion
    n 1: a journey taken for pleasure; "many summer excursions to
         the shore"; "it was merely a pleasure trip"; "after
         cautious sashays into the field" [syn: excursion,
         jaunt, outing, junket, pleasure trip, expedition,
         sashay]
    2: wandering from the main path of a journey [syn: digression,
       excursion]