Stands for "Dual In-Line Memory Module." It is a type of computer memory. A DIMM is a small circuit board that holds memory chips. It uses a 64-bit bus to the memory, whereas a single in-line memory module (SIMM) only has a 32-bit path. This allows DIMMs to transfer more data at once. Because DIMMs have faster data transfer capabilities than SIMMs, they have pretty much replaced SIMMs.