a computer-based and supported library catalog (bibliographic database) designed to be accessed via terminals so that library users may directly and effectively search for and retrieve bibliographic records without the assistance of a human intermediary such as a specially trained member of the library staff.
A computer workstation used search a library's catalog. OPAC can refer to either the actual workstation in the library, or to the interface provided by the library that is accessible from anywhere.
The online version of a library's catalog. See also Catalog.