my short definition of religion is dependence on some form of irrefutable certainty.

this gets a little hazy when dealing with religions that don't examine ontology or epistemology.

and the definition gets rather convoluted when dealing with thelema, discordianism, buddhism, and hinduism.

science and philosophy tend to avoid the irrefutable and/or the certain, but even they cross the line, but hopefully much less so than religions.