A bare unpackaged chip. A die is the square of silicon containing integrated circuits (ICs) that has been cut out of the wafer but not yet packaged. Die is singular; dice is plural. When the dice are packaged they become chips. See
MCM,
wafer and
chip.
Chips on a Wafer
This picture of two ICs still on the wafer shows the various circuits, which have been colored for public presentation. (Image courtesy of Texas Instruments, Inc.)