scram
/skræm/
rhymes with ham, jam, slam
Verb
intransitive
- informalTo leave a place in a hurry; to clear off, usually because you've been told to. "The kids scrammed the moment the neighbor's porch light came on."
transitive
- nuclear powerTo shut down a nuclear reactor suddenly in an emergency, typically by dropping its control rods into the core. "The operators scrammed the reactor when the coolant pressure fell."
Interjection
- informalUsed to order someone to go away at once. "Scram! And don't come back."
Noun
- nuclear powerAn emergency shutdown of a nuclear reactor. "The plant recorded two scrams last year."
Word forms
- scrams
- scrammed
- scramming
Origin
American slang from the 1920s, most likely a shortened form of scramble. The nuclear sense followed in the 1940s, in the early days of reactor research.
A popular story says the nuclear meaning stands for "Safety Control Rod Axe Man", a person said to have stood ready to cut a rope holding a control rod over the first reactor. It's a well-loved legend, but most likely a backronym invented after the word was already in use.
See also
SCRAM (all capitals), short for Salted Challenge Response Authentication Mechanism: a standard way for a program to prove it knows a password without sending the password itself.