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).

