GR translation: physically highballing them about the sky

[Mike Jing]

V85.26-30, P83.13-17   But Edwin Treacle, that most Freudian of psychical
researchers, thinks Slothrop’s gift is psychokinesis. Slothrop is, with the
force of his mind, causing the rockets to drop where they do. He may not be
physically highballing them about the sky: but maybe he is fooling with the
electrical signals inside the rocket’s guidance system.

What does "physically highballing" imply here exactly?