The phrase "small radius" refers to something that has a small measure or distance from the center point of a circle or sphere. It means the distance from the center to the edge is short. Full definition
The hardest challenge is creating complicated shapes with a very small radius of curvature. (sciencedaily.com)
At idle or when the motor is off, the belt should run at the edge of the rear pulley and at a really small radius around the front pulley, as seen in this picture: (mechanics.stackexchange.com)
There's a variety of different powers, including Time Shield (a bubble which heals and stops bullets), Time Dodge (teleport dashing), and Time Stop (small radius which freezes enemies or moving objects) that can be used against foes offensively and defensively. (impulsegamer.com)