segmentation fault

n. [Unix] 1. [techspeak] An error in which a running program attempts to
access memory not allocated to it and core dumps with a segmentation
violation error. This is often caused by improper usage of pointers in the
source code, dereferencing a null pointer, or (in C) inadvertently using a
non-pointer variable as a pointer. The classic example is: inti; scanf( %d
,i);/*shouldhaveused i*/ 2. To lose a train of thought or a line of
reasoning. Also uttered as an exclamation at the point of befuddlement.