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.

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.

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.

1. set boundaries to and delimit

    e.g. mark out the territory

    Synonym: mark out

2. put a check mark on or near or next to

    e.g. Please check each name on the list
           tick off the items
           mark off the units

    Synonym: checkcheck offmarktick offtick