Wiktionary
bradyon
n. (context physics English) A tardyon.
Usage examples of "bradyon".
Then to see how light speed forms a natural barrier separating bradyons (the familiar "slow" particles of our universe, also known as tardyons) from tachyons, imagine that we accelerate a charged particle faster and faster, for example using an electromagnetic field.
Thus if both bradyons and tachyons exist, each is confined to its own velocity region.
The speed of light is a "barrier" that forever separates the world of tachyons from the world of bradyons, and one can never become the other.