I thought about cheating  and going with the obvious choice of A is for Acceleration but in the end I opted for Asymmetric.

Asymmetric acceleration is deployed with units in a single location typically in the same data centre as the servers.  Some people will say that it only requires a single unit, I prefer to say a single HA pair.  Asymmetric acceleration is not limited to HTTP; acceleration available in asymmetric deployments include (but are not limited to):

• Server Load Balancing
• Compression
• Caching
• TCP Optimizations
• SSL Acceleration

(More on these features later in the series - stay tuned). 

With asymmetric deployments all users receive the benefits of the optimizations not just those in locations that have symmetrically deployed endpoint devices or have installed additional client software. 

For more information on asymmetric acceleration check out the Acceleration 102: Asymmetric or Symmetric white paper.