Bindu is the Chakobsa word for "muscle".
The word was typically used by the Bene Gesserit Sisterhood when referring to control of the muscles, and way in which muscles were used.
It was often used in conjunction with prana, which meant "nerve".
Thus, if someone was said to have "prana-bindu" training, it was meant to denote supreme control of nerve and muscles.
'Bindu' in sanskrit refers to a seed visualised in tantric meditation (both hindu and buddhist).
Prana is a sanskrit word for energy. Bindu is a sanskrit word for points. Together they form a reference to the discipline of mastery over the body through its energy points. This is something that the Bene Gesserit deeply study to enhance the physically adept skills over their bodies especially relevant for their controlled breeding program.