Knockback

Knockback means the champion will be knocked back a certain number of squares. If the champion can't be pushed back, the target and what it is knocking back into will both take 5 Physical damage for each square it was supposed to move. (Note fonts and elevated terrain have no HP and thus don't take damage.)

You can predict what direction the champion will knockback by the following chart (originally posted by Linque on the SP knockback guide). It will show what direction the champion will be knocked if the effect originated from any of various locations around the champion.