pinhole

noun

1. A small hole, of a size that could have been made by a pin
2. The aperture in a pinhole camera or camera obscura

   “These [the eyes of the nautilus] are the simplest eyes of any large living animal -- lensless 'pinholes' that project a hazy and rather dim image onto its retinas.”

3. A port left unprotected by a firewall to allow a particular application to gain access to a service.
4. A clipping of pinhole eye, which refers to the compact eye structure associated with intense tropical cyclones.

verb

1. (transitive)To form one or more pinholes in.