an optical device for projecting a beam of light
"The old projector struggled to cast a sharp beam of light across the large white wall during the presentation."
an optical instrument that projects an enlarged image onto a screen
"We set up the projector in the living room to cast the movie onto the white sheet on the wall for our outdoor party."
Someone who devises or suggests a project; a proposer or planner of something.
"The new community center had to wait for months while their chief projector slowly gathered enough volunteers and funding to get the renovation started."
In plain English: A projector is a machine that shines light through an image to display it on a wall or screen so you can watch movies or presentations from far away.
"We rented a projector to show the movie on our living room wall."
Usage: In modern English, the word projector almost exclusively refers to a device that displays images or videos onto a surface. Although it can technically mean someone who plans a project, this usage is now rare and often confused with the more common noun "planner."
The word projector comes partly from the Latin term projector, meaning a person who throws something away, and partly from combining the English verb "project" with the suffix "-or." It entered usage to describe someone or something that projects images or light rather than literally discarding objects.