Dictionary.net

One or more duties that a SPECIALIST or MARKET MAKER must undertake, including taking one side of a purchase or sale ORDER through a proprietary account when the other side cannot be immediately matched, quoting twosided markets at all times, and reporting all executed trades within a predefined time frame. Also known as POSITIVE OBLIGATION. See also INTERPOSITIONING, NEGATIVE OBLIGATION. AFTER HOURS TRADING TRADING in securities that occurs after the formal close of an EXCHANGE, through telephonic networks or ELECTRONIC COMMUNICATION NETWORKS supported by BROKER/DEALERS. In practice only BENCHMARK securities with a broad investor follow trade after hours.