He sees the officer on the street and thinks of ways to take revenge, eventually deciding to bump into him, which he does, finding to his surprise that the officer does not seem to notice that it even happened.
He sees the officer on the street and thinks of ways to take revenge, eventually borrowing money to buy a higher class overcoat and bumping into the officer to assert his equality. To the Underground Man's surprise however, the officer does not seem to notice that it even happened.