To arrest; (especially) to track down and arrest.
To insert (a word, etc.) without making a line break or new paragraph (so that it is not free-hanging).
To use new machinery at less than full speed, preventing damage.
To start a new regime slowly.
To use new machinery at less than full speed, preventing damage. (transitive sense)
To score (a try).
To alter the position of matter to fill vacant space.
(sometimes comparable) Having been run in to seat the parts.
(not comparable) Having been run in before or behind previous text.