Definition of tombstones:
(n) :
A grave marker, a stone slab or similar object marking a person's grave.
(n) :
(mathematics) The symbol "∎" marking the end of a proof.
(n) :
(computing, Microsoft Windows) A marker that takes the place of deleted data, allowing for replication of the deletion across servers etc.
(n) :
(computing) A crashdump.
(n) :
(cardiology) An unusual morphological feature on an electrocardiogram indicative of acute myocardial infarction, characterized by a massive ST elevation.
(n) :
(journalism) A printed advertisement in a newspaper or magazine, typically having unadorned centered text in black and white, enclosed in a simple box.