The Collaborative International Dictionary of English v.0.48:

mockingbird \mockingbird\, mocking bird \mocking bird\n.
   (Zool.),
   A long-tailed gray-and-white songbird of North America
   (Mimus polyglottos), remarkable for its exact imitations of
   the notes of other birds. Its back is gray; the tail and
   wings are blackish, with a white patch on each wing; the
   outer tail feathers are partly white. Originally its range
   was confined mostly to the southern states, but by late 19th
   century it had migrated as far north as New York. The name is
   also applied to other members of thee same and related
   genera, found in Mexico, Central America, and the West
   Indies, such as the blue mockingbird of Mexico, Melanotis
   caerulescens.

   Syn: mocker, Mimus polyglottos .
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

mockingbird
    n 1: long-tailed grey-and-white songbird of the southern United
         States able to mimic songs of other birds [syn:
         mockingbird, mocker, Mimus polyglotktos]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "mockingbird":
   Philomel, ape, bulbul, canary, conformist, copier, copycat,
   copyist, counterfeiter, cuckoo, dissembler, dissimulator, echo,
   echoer, echoist, faker, feathered songster, forger, hypocrite,
   imitator, impersonator, impostor, lark, mavis, mime, mimer, mimic,
   mimicker, mocker, monkey, nightingale, oriole, parrot, phony,
   plagiarist, poll-parrot, polly, polly-parrot, poseur, ringdove,
   sheep, simulator, singing bird, song sparrow, songbird, songster,
   thrush, warbler



The Jargon File (version 4.4.7, 29 Dec 2003):

mockingbird
 n.

    Software that intercepts communications (especially login transactions)
    between users and hosts and provides system-like responses to the users
    while saving their responses (especially account IDs and passwords). A
    special case of Trojan horse.


The Free On-line Dictionary of Computing (30 December 2018):

mockingbird

   Software that intercepts communications (especially login
   transactions) between users and hosts and provides system-like
   responses to the users while saving their responses
   (especially account IDs and passwords).  A special case of
   Trojan horse.

   [Jargon File]