Theory ...(many definitions...see why it is difficult to debate these things?)

1: A well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena

2:A tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena

"a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"; "a scientific possibility that survives experimental testing becomes a scientific theory"

3:A belief that can guide behavior

4:An unproven conjecture.

5: (logic) A set of axioms together with all statements derivable from them.
A theory is consistent if it has a model.