To do something difficult, frustrating, or pointless.
To scratch (something) with claws or fingernails; to claw.
Of a nuclear reactor or some other thing: to shut down, usually because of an emergency.
To leave in a hurry; to go away.
To shut down (a nuclear reactor or, by extension, some other thing) for safety reasons, usually because of an emergency.
A shutdown of a nuclear reactor (or, by extension, some other thing), often done rapidly due to an emergency.
The device used to shut down a nuclear reactor; also, the button or switch used to initiate a shutdown.
A scratch, especially caused by claws or fingernails.