So my main language is Greek and I read english and greek books. Depending on the book/author I may have 2-5 words per page that I may not understand (or at least I want to understand them better). Thus, many times after I finish a page, I use aard2 and either search the word in the english-to-english dictionary or (rarer) in the greek wiktionary for a translation. (For context, I'm reading ~mainly fantasy, sci-fi or dystopian books of the 20th and 21th century and currently I'm on "Croocked kingdom". I haven't dared to try reading a classic book in english.)
The issue is that this effectively slows me down by an extra ~50% time per page and I'm not even very sure that those words are remembered. I could simply keep reading without searching the words up and just use the context to get a vague sense of their meaning (or simply ignore them as they ~usually aren't necessary to the plot), but I think I'd miss on the whole experience by doing this and it doesn't address the underlying issue (being that I don't know english extremely well even if I have C2 and scored high on vocabulary), which will perpetuate the problem. I'd like to note that I have made searching words almost as efficient as it gets by using downloaded dictionaries, so I don't think I can reduce the time I spend looking up words by anything more, at least on paper books.
I'd like to ask anyone who searches up words like me:
Did you eventually reach a point where you learnt enough words this way, that it wasn't that much necessary to use dictionaries anymore? (I'd be kinda satisfied if I could reduce the frequnecy of unknown words to 1 per two pages or something.)
Add an additional step into your word-lookup routine: practice it a little bit. Repeat it several times, preferably out loud and with proper pronunciation, consider the definitions a little bit, and compose an original sentence or two that incorporates the word. Personally I sometimes look up the etymology as well, that stuff just interests me in general though.
This will take a few extra minutes, but will seat the new vocab word in your memory better. It can still sometimes take two or three individual encounters to finally have the word fully remembered, but eventually it does just permanently enter your vocabulary.
You're basically trying to force it from your short-term memory into your long-term memory just like you would with basic schoolwork, using similar techniques.