8 U.S.C. § 1572 - Definitions

(1) Backlog 
The term backlog means, with respect to an immigration benefit application, the period of time in excess of 180 days that such application has been pending before the Immigration and Naturalization Service.

(2) Immigration benefit application 
The term immigration benefit application means any application or petition to confer, certify, change, adjust, or extend any status granted under the Immigration and Nationality Act [8 U.S.C. 1101 et seq.].