vomitorium

As a letter s

is the letter s with a.

As a noun vomitorium is

a passage located behind a tier of seats in an amphitheatre used as an exit for the crowds.

As nouns the difference between vomitorium and vomitory

is that vomitorium is a passage located behind a tier of seats in an amphitheatre used as an exit for the crowds while vomitory is the entrance into a theater or other large public venue, where masses of people are disgorged into the stands; a vomitorium.

As an adjective vomitory is

inducing vomiting; emetic.