An act of refuting or disproving; the disproving of an argument, opinion, testimony, doctrine or theory by argument or countervailing proof; evidence of falseness.
A vocal answer to an attack on one's assertions.
A signal; anything that indicates, or is characteristic of, the presence of something else, especially of something undesirable.
A perceived change in some function, sensation or appearance of a person that indicates a disease or disorder, such as fever, headache or rash; strictly, a symptom is felt or experienced by the patient, while a sign can be detected by an observer.