I had 4 interviews so far with a company. Does this mean I'm rejected?

NO. Unless you get the clear rejection phone call or email, you are NOT rejected.

There are 3 scenarios in your case:

1. They are testing you for more than one position. There are times when a company has more than one position open. You might have skills for more than one position and they want to see where you fit best. Sometimes the positions are in different departments with different managers and each wants to check you to see where you would perform best. It's ok to ask this question if you feel that they are interviewing you too much. They should tell you this information and not keep you in the dark.

2. You are considered for a middle level to senior position and more people need to see you. Getting everybody in the same room at the same time can be intimidating to the candidate. It's not advisable to have one candidate and 4-5 interviewers. Probably they all want to see you to decide.

3. You are being interviewed for a position in a company which requires candidates to go through several interviews and tests befor being hired. For example we hired in our company some French and English Linux engineers. They needed first to be tested over the phone in terms of language skills, then they came to the office for the IT advanced tests, then HR had a meeting with them, then their manager and finally the client who requested to do the final interview.

So, if you have more than one interview, it's not necessarily bad and if you have doubts and you need more information, it's ok to ask.