A whirlpool was a body of swirling water.
In 2266, the B-Gamma Maelstrom was often compared to a whirlpool. (TOS comic: "The Enterprise Mutiny")
The galactic whirlpool, an enormously destructive effect caused by the revolving orbits of two black holes, was compared to the whirlpool effect of a propeller churning through water.
The Bajoran wormhole was often compared to a whirlpool. (DS9 novels: Objective: Bajor, The Heart of the Warrior, The 34th Rule)