What is the meaning of Diapositive?

An image suitable to overlay (superimpose) over another (as for example a gel for an overhead projector, a slide that complements another slide as a superimposition for it, or a digital virtual equivalent of these); its coloration is adjusted to contrast with the underlying image (for example, text may be white instead of black in areas where the background is dark).

slide (used with a projector for projecting images)

slide (of a presentation program)