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).