To solve the given question, we need to identify which pair among the given options least matches with respect to computers. Let's evaluate each option:

1. GigaByte : (1024) × (1024) × (1024) × 8 bits
   • A GigaByte (GB) is indeed a measure of digital information storage, and therefore, the binary computation is correct. However, this representation adds an extra step of multiplying by 8, which is incorrect. In computers, 1 GigaByte is actually defined as 1024 × 1024 × 1024 bytes.
2. CRT : Cathode Ray Tube
   • CRT stands for Cathode Ray Tube, which is a technology used in older television sets and computer monitors. It uses electron beams to create images on the screen. This is a correct match.
3. ROM : Rapid Online Memory
   • ROM is a hardware component in computers that stands for Read-Only Memory, not Rapid Online Memory. It is a type of non-volatile storage that contains essential firmware and software for booting up the computer. Thus, this option is incorrect and does not match the reality of computer terminology.
4. CPU : Central Processing Unit
   • CPU accurately stands for Central Processing Unit, which is the primary component of a computer responsible for processing instructions and performing the logical and arithmetic operations. This is a correct match.

Upon evaluation, the option "ROM: Rapid Online Memory" does not correctly describe the actual term associated with computers. The correct expansion for ROM is Read-Only Memory, making this the least matching pair.

Therefore, the correct answer is ROM : Rapid Online Memory.