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.
by
Hamad Al Ali , Security Superintendent , National Aviation Services
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.