Feel free to take a stab at it.
A theory is an established paradigm that explains all or much of the data we have and offers valid predictions that can be tested.
in science, a body of descriptions of knowledge is usually only called a theory once it has a firm empirical basis, i.e., it
1. is consistent with pre-existing theory to the extent that the pre-existing theory was experimentally verified, though it will often show pre-existing theory to be wrong in an exact sense,
2. is supported by many strands of evidence rather than a single foundation, ensuring that it probably is a good approximation if not totally correct,
3. makes predictions that might someday be used to disprove the theory,
4. is tentative, correctable and dynamic, in allowing for changes to be made as new data is discovered, rather than asserting certainty, and
5. is the most parsimonious explanation, sparing in proposed entities or explanations, commonly referred to as passing Occam's Razor.