a. 1. Clothed; robed; wearing vestments. “The vested priest.” Milton. [ 1913 Webster ]

2. (Law) Not in a state of contingency or suspension; fixed; as, vested rights; vested interests. [ 1913 Webster ]

Vested legacy (Law), a legacy the right to which commences in praesenti, and does not depend on a contingency; as, a legacy to one to be paid when he attains to twenty-one years of age is a vested legacy, and if the legatee dies before the testator, his representative shall receive it. Blackstone. --
Vested remainder (Law), an estate settled, to remain to a determined person, after the particular estate is spent. Blackstone. Kent. [ 1913 Webster ]

. 1. a special personal interest, usually financial, in an existing system, law, or institution, which hinders a person from making objective decisions regarding that system, law, or institution. A vested interest may be one which benefits a relative, or, in an extended sense, one which defends a person's own reputation or previously expressed views. [ PJC ]

2. a right given to an employee by a pension plan, which cannot be taken away. [ PJC ]

3. pl. the persons, corporations, or other groups which benefit most (usually financially) from the existing system of institutions, laws, and customs. [ PJC ]

. In Ireland, a national school which has been built by the aid of grants from the board of Commissioners of National Education and is secured for educational purposes by leases to the commissioners themselves, or to the commissioners and the trustees. [ Webster 1913 Suppl. ]