Falsifiability is the logical possibility that an assertion or theory can be contradicted by an observation or the outcome of a physical experiment.  The term "falsifiable" does not mean something is made false, but if it is false, it can be shown by observation or experiment.

Some philosophers (ie, Karl Popper) used falsifiability as the key criterion between what is and what is not genuinely scientific.  That a theory can only be considered scientific if and only if it is falsifiable.  Otherwise it is a "non-testable hypothesis".

The position of the institutional philosophic and scientific community is that any idea or belief that can only be subjectively experienced is unfasifiable.  For example, the belief in God or a supernatural being, according to the theory of falsifiability, is unfasifiable.

The Fallacy of Falsifiability
In Quantum Questions, Integral philosopher, Ken Wilber, keenly points out the subtle fallacy of falsifiability logic – that all domains are open to experiential disclosure.  That all experiences are valid, from the sensory to the psychological and to the  religious.

Recognizing this openness is paramount in building a bridge from science to religion

If the religious knowledge-claim is dogmatic, idiosyncratic or a personal belief, it may or may not be valid, however if it doesn’t pass the basic scientific criteria, then it is non-science (non-testable knowledge-claim).