SIMM
Short for Single In-line Memory Module, SIMM is a circuit board that holds six to nine memory chips per board, the ninth chip usually an error checking chip (parity or non parity) and were commonly used with Intel Pentium or Pentium compatible motherboards. SIMMs are rarely used today have have been widely replaced by DIMMs. Below is a graphic illustration of a 4MB SIMM as well as a diagram pointing out the important features of a SIMM.
Also see: Bank, Memory definitions, RAM