The Collaborative International Dictionary of English v.0.48:

Pathologic \Path`o*log"ic\, Pathological \Path`o*log"ic*al\, a.
   [Gr. ?: cf. F. pathologique.]
   1. Of or pertaining to pathology.
      [1913 Webster]

   2. (Med.) caused by or due to disease; abnormal; morbid; as,
      pathological tissue; a pathological condition.
      [Webster 1913 Suppl.] -- Path`o*log"ic*al*ly, adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pathological
    adj 1: of or relating to the practice of pathology;
           "pathological laboratory" [syn: pathological,
           pathologic]
    2: caused by or evidencing a mentally disturbed condition; "a
       pathological liar"; "a pathological urge to succeed"
    3: caused by or altered by or manifesting disease or pathology;
       "diseased tonsils"; "a morbid growth"; "pathologic tissue";
       "pathological bodily processes" [syn: diseased, morbid,
       pathologic, pathological]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "pathological":
   bad, cankered, contaminated, diseased, gangrened, gangrenous,
   infected, morbid, mortified, peccant, poisoned, septic,
   sphacelated, tainted, ulcerated, ulcerous, unhealthy, unsound,
   unwholesome



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

pathological
 adj.

    1. [scientific computation] Used of a data set that is grossly atypical of
    normal expected input, esp. one that exposes a weakness or bug in whatever
    algorithm one is using. An algorithm that can be broken by pathological
    inputs may still be useful if such inputs are very unlikely to occur in
    practice.

    2. When used of test input, implies that it was purposefully engineered as
    a worst case. The implication in both senses is that the data is
    spectacularly ill-conditioned or that someone had to explicitly set out to
    break the algorithm in order to come up with such a crazy example.

    3. Also said of an unlikely collection of circumstances. ?If the network is
    down and comes up halfway through the execution of that command by root,
    the system may just crash.? ?Yes, but that's a pathological case.? Often
    used to dismiss the case from discussion, with the implication that the
    consequences are acceptable, since they will happen so infrequently (if at
    all) that it doesn't seem worth going to the extra trouble to handle that
    case (see sense 1).


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

pathological

   1. [scientific computation] Used of a data set that is grossly
   atypical of normal expected input, especially one that exposes
   a weakness or bug in whatever algorithm one is using.  An
   algorithm that can be broken by pathological inputs may still
   be useful if such inputs are very unlikely to occur in
   practice.

   2. When used of test input, implies that it was purposefully
   engineered as a worst case.  The implication in both senses is
   that the data is spectacularly ill-conditioned or that someone
   had to explicitly set out to break the algorithm in order to
   come up with such a crazy example.

   3. Also said of an unlikely collection of circumstances.  "If
   the network is down and comes up halfway through the execution
   of that command by root, the system may just crash."  "Yes,
   but that's a pathological case."  Often used to dismiss the
   case from discussion, with the implication that the
   consequences are acceptable, since they will happen so
   infrequently (if at all) that it doesn't seem worth going to
   the extra trouble to handle that case (see sense 1).

   [Jargon File]