An orifice is any opening, mouth, hole or vent, as of a pipe, plate, or a body.
- Body orifice, any opening in the body of an animal
- Orifice plate, a device used for measuring the volumetric flow rate. Orifice plate is choke plate, working as restriction function.
- Calibrated orifice, a restriction placed into a system of pipes to set the flow rate
- Back Orifice, a controversial computer program designed for remote system administration