If something's inconclusive, that means it doesn't lead to a conclusion or a resolution. Inconclusive often describes scientific results. If your data about a flu outbreak is inconclusive, then your results don't prove anything.
A good way to remember the meaning of inconclusive is to look at the root word conclusive, which means "definitive, decisive, and convincing." When you add in- — which means "not" — to the front of conclusive, you get a word that means "not definitive." When something's inconclusive, it doesn't resolve your questions and leaves room for debate. If you're a detective, the last thing you want to hear is that your evidence is inconclusive.