mark something off

Từ điển Oxford Advanced Learner 8th

▪ I. ˌmark sthˈoff derived
to separate sth by marking a line between it and sth else
•The playing area was marked off with a white line.
Main entry: ↑mark_derived
 
▪ II. ˌmark sb/sth ˈoff (from sb/sth) derived
to make sb/sth seem different from other people or things
•Each of London's districts had a distinct character that marked it off from its neighbours.
Main entry: ↑mark_derived