Definition
To deliberately slight or snub someone.
Origins
Possibly coined by Sir Walter Scott in 1816, from give someone the cold shoulder.
How People Actually Use It
The act of a person completely disregarding or ignoring another. This can be caused by a few things: 1. A person is in a bad mood and doesn't feel like talking to anyone. 2. A person says something so incredibly stupid that it doesn't deserve a response, thus the person is ignored.
"I wanted to be friends with my ex, but she gave me the cold shoulder."
Source: Urban Dictionary