Well I'm not entirely sure but I think it's a small narrow cut.
Volcanoes occur in long, narrow belts because that's were the pate boundaries are.
Fault
Ria is a long narrow inlet.
misericorde - a long, narrow knife
A long narrow and very deep canyon where the ocean floor bends down toward the mantle is called an ocean trench. This is caused by two plates pulling apart.
crack!
slit
wide
A narrow opening refers to a small or restricted space through which something can pass. It typically implies a limited width or aperture that may require things to be squeezed or fitted carefully through it. Examples include a crack in a wall or a tight passageway between two objects.
3d. pers. sing. pres. of Slide., of Slit, To cut lengthwise; to cut into long pieces or strips; as, to slit iron bars into nail rods; to slit leather into straps., To cut or make a long fissure in or upon; as, to slit the ear or the nose., To cut; to sever; to divide., A long cut; a narrow opening; as, a slit in the ear.
Slot
A narrow fissure is a long, narrow opening or crack in a surface, typically seen in rock formations or the Earth's crust. These fissures can be a result of geological processes such as tectonic movements or erosion.
The pharynx is the narrow opening at the back of the mouth. It is part of both the digestive system and the respiratory system.
A narrow gap or crack in a rock is commonly referred to as a fissure. This term describes a long, narrow opening in the rock where it has split or fractured. Fissures can vary in size and depth.
spinal cord
The Mediterranean
Chanelled into a narrow opening.