1. A data compression technique that reduces the size of a file without sacrificing any original data; used by programs, such as Stacker to compress all the program and document files on a hard disk. In lossless compression, the expanded or restored file is an exact replica of the original fie before it was compressed, while in lossy comprssion, data is lost in a way imperceptible to humans. Lossless compression is suitable for text and computer code, while lossy compression is good mainly for shrinking audio and graphics files. From QUECID