an opening for the escape of a gas or liquid or for the relief of pressure, e.g.:
the anus, esp of the cloaca of a bird or reptile
an outlet of a volcano; = fumarole
formerly, a hole at the breech of a gun through which the powder was ignited
a means of escape or release; an outlet
give vent to something
to give strong expression to one's feelings, etc
ventless adj
[Middle English venten, prob from early French esventer to expose to the air, from es- ex-1 + vent wind, from Latin ventus]