Genital orifice not covered by an operculum.

The water is expelled from the branchial chambers by one or two tubes opening by one orifice in most Batrachians.

He was sprouting tubes from every orifice - and then some.

He remarked that the flow of water from an orifice depends not only on the magnitude of the orifice itself, but also on the height of the water in the reservoir; and that a pipe employed to carry off a portion of water from an aqueduct should, as circumstances required, have a position more or less inclined to the original direction of the current.

He had discovered a contraction in the vein of fluid (vena contracta) which issued from the orifice, and found that, at the distance of about a diameter of the aperture, the section of the vein was contracted in the subduplicate ratio of two to one.