I try to figure out what it means from a combination of context and etymological guesswork, then check it a dictionary. If it’s a person or region or concept I’m unfamiliar with that isn’t covered directly or in notes, I hit the encyclopedia or atlas (well, Wikipedia and mapping software, these days.)

That’s how my father taught me to deal with stuff I didn’t understand when I was a kid and I’ve been doing that ever since. It interrupts the flow far less than having to set it aside for other demands on my time, so it’s not that big a deal.

We always had good dictionaries and encyclopedias on hand. Now, of course, it’s all online or downloadable.

One of the reasons I love eReaders is direct access to dictionary, translations, and Wikipedia.