Source : Webster's Revised Unabridged Dictionary (1913)

Addle \Ad"dle\, v. t. & i. [imp. & p. p. {Addled}; p. pr. & vb.
   n. {Addling}.]
   To make addle; to grow addle; to muddle; as, he addled his
   brain. ``Their eggs were addled.'' --Cowper.