A person who only does/buys things because everyone else has so is therefore following the crowd. Not only can you just call a person a 'sheep', you can also give subtle hints (see example 2)
Example 1
Person 1: Look at her with her new jacket.
Person 2: She is such a sheep.
Example 2
Person 1: Hey, do you like my new phone?
Person 2: Baaaaaa
5👍 1👎