Definition 1: Settlement is an act that discharges obligations in respect of funds or securities transfers between two or more parties. See also final settlement, gross settlement system, net settlement, net settlement system.
Definition 2: Settlement is the completion of a transaction, wherein the seller transfers securities or financial instruments to the buyer and the buyer transfers money to the seller. A settlement may be final or provisional.
Source: BIS Glossary of terms used in payments and settlement systems