n. When a fatal error occurs (esp. a segfault) the immediate cause may be that a pointer has been trashed due to a previous fandango on core. However, this fandango may have been due to an *earlier* fandango, so no amount of analysis will reveal (directly) how the damage occurred. "The data structure was clobbered, but it was secondary damage."
By extension, the corruption resulting from N cascaded fandangoes on core is 'Nth-level damage'. There is at least one case on record in which 17 hours of grovelling with 'adb' actually dug up the underlying bug behind an instance of seventh-level damage! The hacker who accomplished this near-superhuman feat was presented with an award by his fellows.