If you say that someone is behaving like something or someone else, you mean that they are behaving in a way that is typical of that kind of thing or person. Like is used in this way in many fixed expressions, for example, to cry like a baby and to watch someone like a hawk. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.