submarine

Being, relating to, or made for use underwater, especially beneath the sea.

Near-synonym: submerged (synonymous in "being underwater" sense)

[…] a Chorus of Sea-nymphs, who[…] arrive, in a winged car, from the submarine palace of their father Oceanus.

Hidden or undisclosed.

a submarine patent

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.

A boat that can go underwater.

Me: *staring out window* looks like rain Submarine captain: what Me: but like more

Alternative form of submarine sandwich.

A pitch delivered with an underhand motion.

Any submarine plant or animal.

A stowaway on a seagoing vessel.

To operate or serve on a submarine.

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.”

To sink or submerge oneself.

The second their center snapped the ball, I submarined between the big guy's legs and tackled the halfback.

Ten days later, the full force of what happened crushed me. I submarined into the depths of disillusionment.

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.