nonlinear

nonlinear adj.  [scientific computation] 1. Behaving in an
   erratic and unpredictable fashion; unstable.  When used to describe
   the behavior of a machine or program, it suggests that said machine
   or program is being forced to run far outside of design
   specifications.  This behavior may be induced by unreasonable
   inputs, or may be triggered when a more mundane bug sends the
   computation far off from its expected course.  2. When describing
   the behavior of a person, suggests a tantrum or a {flame}.
   "When you talk to Bob, don't mention the drug problem or he'll go
   nonlinear for hours."  In this context, `go nonlinear' connotes
   `blow up out of proportion' (proportion connotes linearity).