surface-to-air missile: a guided missile fired from land or shipboard against an airborne target
guided missile: a rocket-propelled missile whose path can be controlled during flight either by radio signals or by internal homing devices
placebo effect: any effect that seems to be a consequence of administering a placebo; the change is usually beneficial and is assumed result from the person's faith in the treatment or preconceptions about what the experimental drug was supposed to do; pharmacologists were the first to talk about placebo effects but now the idea has been generalized to many situations having nothing to do with drugs