a strong reason for wanting something to happen because you will gain from it:
Since he owns the strip of land, Cook has a vested interest in the project being approved.
the groups of people who will gain from a plan, project, proposal etc:
The proposal faces tough opposition from powerful vested interests.
vested rights, powers, property etc belong to you and cannot be removed:
Shareholders have a vested right to 10% per annum.
having full rights to own or have something
become/get vested (in something)
He only took the job to get vested in the pension fund.