Example of a Bottleneck: Your GPU is higher-end compared to your processor, but your processor isn't powerful enough and prevents your GPU from working at full potential. This is also known as bootlegging.
A bottleneck is a point of congestion in a production system (such as an assembly line or a computer network) that occurs when workloads arrive too quickly for the production process to handle.
Online friends are 1337 for fuelling their SLI/CrossFire rig with a three Nvidia 480 GTX in SLI that cost $1,500 at Newegg.
Their cheap friends get pwnd by their enemy, but afterwards bitch about a bottleneck in their shit rig.
A Bottleneck Gamers' computer is upgraded in spring, when technology trends secure an extreme re-branding and marketing for teenagers and/or the basement trolls.