The Collaborative International Dictionary of English v.0.48:

Eavesdrop \Eaves"drop`\ ([=e]vz"dr[o^]p`), v. i. [Eaves + drop.]
   To stand under the eaves, near a window or at the door, of a
   house, to listen and learn what is said within doors; hence,
   to listen secretly to what is said in private.
   [1913 Webster]

         To eavesdrop in disguises.               --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Eavesdrop \Eaves"drop`\, n.
   The water which falls in drops from the eaves of a house.
   [1913 Webster]

WordNet (r) 3.0 (2006):

eavesdrop
    v 1: listen without the speaker's knowledge; "the jealous man
         was eavesdropping on his wife's conversations" [syn:
         listen in, eavesdrop]

The Devil's Dictionary (1881-1906):

EAVESDROP, v.i.  Secretly to overhear a catalogue of the crimes and
vices of another or yourself.

    A lady with one of her ears applied
    To an open keyhole heard, inside,
    Two female gossips in converse free --
    The subject engaging them was she.
    "I think," said one, "and my husband thinks
    That she's a prying, inquisitive minx!"
    As soon as no more of it she could hear
    The lady, indignant, removed her ear.
    "I will not stay," she said, with a pout,
    "To hear my character lied about!"
                                                        Gopete Sherany