A bird, the black tern.
The tail of an animal; now used only of the tail of a dog.
The hinder part of anything.
The post of management or direction.
The rear part or after end of a ship or vessel.
Grim and forbidding in appearance.
Having a hardness and severity of nature or manner.
To propel or move backward or stern-first in the water.
Easy to deal with or manage
Capable of being easily led, taught, or managed.
Capable of being shaped; malleable.
Sufficiently operationalizable or useful to allow a mathematical calculation to proceed toward a solution.
Algorithmically solvable fast enough to be practically relevant, typically in polynomial time.