Source : Webster's Revised Unabridged Dictionary (1913)

Lengthy \Length"y\ (-[y^]), a. [Compar. {Lengthier}
   (-[i^]*[~e]r); superl. {Lengthiest}.]
   Having length; rather long or too long; prolix; not brief; --
   said chiefly of discourses, writings, and the like. ``Lengthy
   periods.'' --Washington. ``Some lengthy additions.'' --Byron.
   ``These would be details too lengthy.'' --Jefferson. ``To cut
   short lengthy explanations.'' --Trench.

Source : WordNet®

lengthy
     adj : relatively long in duration; tediously protracted; "a
           drawn-out argument"; "an extended discussion"; "a
           lengthy visit from her mother-in-law"; "a prolonged and
           bitter struggle"; "protracted negotiations" [syn: {drawn-out},
            {extended}, {prolonged}, {protracted}]
     [also: {lengthiest}, {lengthier}]

lengthier
     See {lengthy}