1a strong covering holding the pages of a book together.
2 [mass noun] fabric cut or woven in a strip, used for binding the edges of a piece of material.
3 (also ski binding) Skiing a mechanical device fixed to a ski to grip a ski boot, especially either of a pair used for downhill skiing which hold the toe and heel of the boot and release it automatically in a fall.
4 [mass noun] (in Chomskyan linguistics) the relationship between a referentially dependent noun (such as a reflexive) and the independent noun phrase which determines its reference.
5 [mass noun] the action of fastening or holding together, or of being linked by chemical bonds:the binding of antibodies to cell surfaces
(of an agreement or promise) involving an obligation that cannot be broken:business agreements are intended to be legally binding
binding in other Oxford dictionaries
Definition of binding in the US English dictionary