A piece of software used to automate interaction between two computer systems through the terminal interface (designed for human use) of one of those systems.
Typically, the screen scraper interacts with terminal emulation software to generate input to and process output from the "host" system through terminal screens. Screen scrapers are advantageous when modifications to the host system are undesireable, when it is desireable to make use of the existing business and data integrity logic on the host, and when no other (peer-to-peer) interface method is available.
Some products employ screen scraping combined with additional functionality which provides a DBMS-like or other specialised interface to the host. The host system is often called a "legacy system" because it usually the older of the systems involved and based on older technology.