What is Being Biased or Biased?

Exact meaning or definition of biased or being biased ?

Biasness is one of the basic human tendencies as people are mostly influenced by someone or develop an opinion on the basis of their preoccupied notions and beliefs.

For instance there is a person in your peer group whom you like or do not. So, whenever that specific person try to comment or give his/her views regarding any matter you will perceive them according to already existing schema about that person and behave accordingly.