A useful word that is often used by a pedant
to let you know that, really, you shouldn't talk at all because you are a mere subset of their knowledge and a flawed one at that
If you find yourself starting sentences with this or similar phrases even if you are totally right, take a look at your motivations. You should realize that you don't have to have the last word, even when they are tantalizingly wrong. If that is the case, they are hanging themselves and it is discourteous of you to pull on their feet.
Recovering pedant #8783217