submarine

Etymology

sub- + marine.

adj

1. Existing, relating to, or made for use beneath the sea.
   […] a Chorus of Sea-nymphs, who[…] arrive, in a winged car, from the submarine palace of their father Oceanus. 1908, Edmund Doidge Anderson Morshead, Four Plays of Aeschylus, Introduction, page xiv
2. Hidden or undisclosed.
   a submarine patent
3. (baseball) Of a pitch, thrown with the hand lower than the elbow.
   When Peterson saw the unusual pitching motion of Kent Tekulve—the submarine pitcher who threw baseballs as though they were coming right out of the rubber slab on the mound—he was the first of many who tried to change Tekulve's delivery. 2005, John McCollister, Tales from the 1979 Pittsburgh Pirates: Remembering "The Fam-A-Lee", page 109

noun

1. A boat that can go underwater.
2. A kind of sandwich made in a long loaf of bread.
3. (baseball) A pitch delivered with an underhand motion.
4. Any submarine plant or animal.
5. (informal) A stowaway on a seagoing vessel.

verb

1. (intransitive) To operate or serve on a submarine.
2. (transitive) To torpedo; to destroy with a sudden sneak attack.
   We’re really at the point of chicken, where the Fed is trying to ward off inflation without submarining the economy. April 13, 2007, The Associated Press, “Shares Up as Investors Ponder Retail Data”, in New York Times
3. (intransitive, sometimes figurative) To sink or submerge oneself.
   The second their center snapped the ball, I submarined between the big guy's legs and tackled the halfback. 2003, Homer H. Grantham, Thunder in the Morning: A World War II Memoir, page 1
   Ten days later, the full force of what happened crushed me. I submarined into the depths of disillusionment. 2013, Gordon MacDonald, Building Below the Waterline, page 234
4. (intransitive, automotive) To slide forwards underneath one's seat belt (during a crash or sudden stop).
   The seatback should always be up while driving so that the occupant doesn't submarine and potentially suffer severe internal injury.