If ir 2as a novel you probably b9ught the footnoted edition. Or You noted the bit that didn't make sense (post stick or noted notebook) and looked it up later. Or you did read it with a dictionary/bible/encyclopaedia to hand
I learned several languages in my teens and early 20s before the internet, and so we looked up words in pocket dictionaries or waited until we had access to a larger dictionary. Or if it was academic reading, we would go and sit in the library and use resources there (including microfiches of old newspapers etc)
I worked in the local reference library one summer whilst s student. People could phone up and ask us to look stuff up for them, think it was capped at 5 or 6 questions a day per person. We’d get a lot of repeats of the same question, e.g. questions on radio quizzes, so we wrote all q’s and a’s for the day down on a pad by the phone.
Dictionaries, & we had the complete Encyclopedia Britannica at home.
I remember one of the broadsheets used to do a big literary quiz every summer & my DM & I would be researching all over the place. That probably wouldn't be so much fun now - the sense of achievement when we managed to track down an obscure quote was much bigger pre-Google!
I remember when I learned French, German, and Spanish, the Internet really wasn't popular than at all. So, with my visual impairment, I would have to try and find a very large print dictionary. I was living in the US, and I remember we had to order a French dictionary from the are in IB because we couldn't find one in the US. I had some audiobooks in Spanish, and since I was living in Florida I had access to things like Spanish television. A lot of my classmates were also from Latin America, so if I didn't know something, I would ask them. I have it that I still used today in a lot of cases. You learned some pretty good stuff just by asking other people. Anyway, that was how we did things then.
I’ve still got the massive 2-volume dictionary my grandparents gave my DM when she graduated uni in the early 80s. I used to have a great time looking things up in it and have great hopes of my DC’s education being enriched by having it around. I fear they will see me as hopelessly antiquated in this aim....
Library. I didn't have the internet at home til I was 27. (I'm 36 now.) I had encyclopedias, thesaurus etc and took a lot of books out of the library. I've still got my grandma's big household encyclopedia. Everything from how to make rice pudding to setting a broken leg in there!
Ask someone, dictionary or guess by context. To be honest I don't tend to read the sort of novels that require me to look stuff up much though. For foreign language learning it was all textbooks and dictionaries.
As others have said we had books at home or the library. When doing my degree if you wanted a journal article you had to look through a huge book of keywords and cross reference and then go and find each individual article.
Whilst it is so easy now, I think lots of skills are being lost.