n A smooth surface, usually made of glass with reflective material painted on the underside, that reflects light so as to give an image of what is in front of it.
n (figuratively) an object, person, or event that reflects or gives a picture of another.
n (computing) An exact copy of a data set, especially a website.
v (transitive) Of an event, activity, behaviour, etc, to be identical to, to be a copy of.
v (context|computing|transitive) To create something identical to (a web site, etc.).