An anti-ballistic missile (ABM) is a surface-to-air missile designed to counter ballistic missiles (see missile defense). Ballistic missiles are used to deliver nuclear, chemical, biological or conventional warheads in a ballistic flight trajectory. The term "anti-ballistic missile" is a generic term conveying a system designed to intercept and destroy any type of ballistic threat, however it is commonly used for systems specifically designed to counter intercontinental ballistic missiles (ICBMs).