Security is the guarantee for the protection of life and property in favour of a human being to live in peace and harmony as per the dictate of a normal society against violence, fear and hostility
As IT Security specialist I prefer the definition of the Institute for Security and Open Methodologies (ISECOM):
Security provides "a form of protection where a separation is created between the assets and the threat." These separations are generically called "controls," and sometimes include changes to the asset or the threat.
Security is the degree of resistance to, or protection from, harm. It applies to any vulnerable and valuable asset, such as a person, dwelling, community, nation, or organization.