n.
1.an event in which one thing is substituted for another
2.the act of furnishing an equivalent person or thing in the place of another
3.someone who takes the place of another person
4.a person or thing that takes or can take the place of another
5.filling again by supplying what has been used up
6.a person who follows next in order
Idiom of the Day
to the core
all the way through, basically
The local government is corrupt to the core and everybody wants the mayor to leave office.