vent

About 3.23 uses per million words.

Meaning

noun An opening through which gases, especially air, can pass.
the vent of a cask; the vent of a mould
noun A small aperture.
noun An opening in a volcano from which lava or gas flows.
noun A rant; a long session of expressing verbal frustration.
noun The excretory opening of lower orders of vertebrates; cloaca.
noun A slit in the seam of a garment.
noun The opening at the breech of a firearm, through which fire is communicated to the powder of the charge.
noun In steam boilers, a sectional area of the passage for gases divided by the length of the same passage in feet.