noun
A device that projects photographic slides onto a screen. Common in educational and presentation settings before digital projectors became widespread.
昔の授業では、スライド映写機を使って写真を見せていた。
In old classes, they used a slide projector to show photos.
プロジェクター is a general term for digital projectors, while スライド映写機 specifically refers to an analog slide projector.
Compound of スライド (slide) and 映写機 (projector). 映写機 itself is a Sino-Japanese word combining 映 (project) and 写 (copy) with 機 (machine).