anything that is open or submissible to one or more objective attempts to invalidate it.

Something that is at least theoretically open to invalidation.

able to be proven false, and therefore testable; as, most religious beliefs are not falsifiable, and are therefor outside the scope of experimental science.

Capable of being falsified, counterfeited, or corrupted.

capable of being tested (verified or falsified) by experiment or observation

A Boolean expression is falsifiable if there exists an interpretation of it under which it evaluates to False.