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]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "eavesdrop":
   attend, attend to, auscultate, be all ears, bend an ear, bug,
   cock the ears, examine by ear, give attention, give audience to,
   give ear, hark, hear, hear out, hearken, heed, intercept,
   lend an ear, listen, listen at, listen in, listen to, overhear,
   pry, sit in on, snoop, spy, tap, wiretap



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