The Collaborative International Dictionary of English v.0.48:

Nuisance \Nui"sance\, n. [OE. noisance, OF. noisance, nuisance,
   fr. L. nocentia guilt, fr. nocere to hurt, harm; akin to
   necare to kill. Cf Necromancy, Nocent, Noxious,
   Pernicious.]
   That which annoys or gives trouble and vexation; that which
   is offensive or noxious.
   [1913 Webster]

   Note: Nuisances are public when they annoy citizens in
         general; private, when they affect individuals only.
         [1913 Webster]

WordNet (r) 3.0 (2006):

nuisance
    n 1: (law) a broad legal concept including anything that
         disturbs the reasonable use of your property or endangers
         life and health or is offensive
    2: a bothersome annoying person; "that kid is a terrible pain"
       [syn: pain, pain in the neck, nuisance]