engine - technical definition

(1) A specialized processor, such as a graphics processor. Like any engine, the faster it runs, the quicker the job gets done. See graphics engine and printer engine.

(2) Software that performs a very specific and repetitive function in contrast to an application that has many functions offered to the user. For example, a "search engine" or "database engine" responds to user queries over and over again. An "SMTP engine" just forwards mail when required. A "dictionary engine" looks up words. See search engine and database engine.