: the placement of one thing above or on top of another
The principle used to determine whether one sedimentary rock is older than another is very simple, and is known as the law of superposition. Here is an example: A deposit of mud laid down this year in, say, the Gulf of Mexico will rest on top of a layer that was deposited last year. Sheldon Judson and Marvin E. Kauffman
especially, physics: the combination of two distinct physical phenomena of the same type (such as spin or wavelength) so that they coexist as part of the same event
Schrödinger perversely suggested that until the box was opened and the outcome of the experiment observed, the particle must remain suspended in a superposition of two states: simultaneously going through both holes. George Johnson
In a quantum computer, however, the "transistors" remain in a superposition of 0 and 1 … Philip Yam