Disulfide Bridge Definition:

The group that is formed when two cysteine residues of a polypeptide or protein are joined together.

Disulfide Bridge Explained:

The single covalent bond formed from the coupling of thiol groups, especially of cysteine residues.
The linkage formed by the oxidation of two SH groups, each attached to a cysteine, stabilizing the structure of many protein molecules (during protein synthesis)