1. A mutual or reciprocal action; interacting.
2. (Physics) The transfer of energy between elementary particles or between an elementary particle and a field or between fields; mediated by gauge bosons; SYN. fundamental interaction.

A covering either permanent or temporary: as an ornamental veneer; a decorative and contrasting design or article placed on top of a plain one; a transparent sheet containing graphic matter to be superimposed on another sheet

Act of placing one thing above or on top of another; act of adding to; act of combining in such a way that both images are seen simultaneously (Television, Film)

ETYM Cf. French superposition. Related to Super-, and Position.
The act of superposing, or the state of being superposed.