tombstone

A headstone marking a person's grave.

The symbol "∎" marking the end of a proof.

A marker that takes the place of deleted data, allowing for replication of the deletion across servers etc.

A crashdump.

An unusual morphological feature on an electrocardiogram indicative of acute myocardial infarction, characterized by a massive ST elevation.

To take part in tombstoning: to jump into the sea, etc. from a cliff or other high point so as to enter the water vertically straight.

For a surfboard to stand upright half-submerged in the water (like a tombstone, above) because the surfer is underwater with his or her legrope pulled tight. Often this indicates a surfer in difficulty, either held down by the power of a wave or unconscious and unable to get to the surface.

To replace (an object or data) with a tombstone marker.