Multibit flip-flop
Beginner
Several one-bit memories packed into one block so they can share wiring.
Novice
A library cell that holds two, four or more flip-flops side by side and shares one clock input and its internal clock circuitry among them, which saves clock power.
Expert
Banking single-bit flip-flops into multibit cells shares the internal clock buffers, lowering clock-pin capacitance and clock power and sometimes area. It happens in synthesis when the library has the cells and the bits are related, or at placement, where the tool knows which flip-flops sit close together.
Explained in Logic synthesis (Design Flow).