Definition from Nolo’s Plain-English Law Dictionary

1) To finish, carry out, or perform as required, as in fulfilling one's obligations under a contract, plan, or court order.
2) To complete and otherwise make valid a document, such as a will, deed, or contract, for example by signing it and having it notarized.
3) To put someone to death pursuant to a court-rendered sentence (capital punishment).
4) To murder or assassinate.

Definition provided by Nolo’s Plain-English Law Dictionary.