1. (用线)画出，圈出
If you mark off a piece or length of something, you make it separate, for example by putting a line on it or around it.
e.g. He used a rope to mark off the circle...
他用绳子把那个圈围了起来。
e.g. Read the text through and mark off the sections you find particularly applicable.
通读全文，画出你认为最有用的段落。
2. 使区别于;使突出
If a particular quality or feature marks someone or something off from other people or things, it is unusual and makes them obviously different.
e.g. Her clothes, of course, marked her off from a great number of the delegates at the conference...
她的穿戴显然使她有别于与会的许多其他代表。
e.g. The traditionalist influences within the navy marked it off as a rather old-fashioned institution.
传统势力在海军内部的影响使其显得像是一个极其守旧的机构。
3. (用画线的方式)划去，勾销
If you mark off a date on a calendar or an item on a list, you put a line through it or next to it, in order to show that it has been completed or dealt with.
e.g. He marked off the days on a calendar...
他划去日历上的日期。
e.g. Miss Hoare called out names and marked them off.
霍尔小姐点名后把它们一一划掉。