n. pl. se·cu·ri·ties 1. Freedom from risk or danger; safety.
2. Freedom from doubt, anxiety, or fear; confidence.
3. Something that gives or assures safety, as:
a. A group or department of private guards: Call building security if a visitor acts suspicious.
b. Measures adopted by a government to prevent espionage, sabotage, or attack.
c. Measures adopted, as by a business or homeowner, to prevent a crime such as burglary or assault: Security was lax at the firm's smaller plant.
d. Measures adopted to prevent escape: Security in the prison is very tight.
4. Something deposited or given as assurance of the fulfillment of an obligation; collateral.
5. One who undertakes to fulfill the obligation of another; a surety.
6. A financial instrument, such as a stock or bond, representing rights of ownership or creditorship and often traded in secondary markets.