What is "retrimming"

Usage examples of "retrimming".

So Grafton was turning as he changed configuration-slowing, retrimming and trying to maintain a precise altitude, all at the same time.

His quill needed retrimming, and he had managed to ink his fingers, and by scrubbing bewilderedly in his spiky, straw-coloured fringe of hair had left smudges on both his eyebrow and his crown.