How do we access the meanings of words? Great question! I’m not sure we can down to the root of the matter, since there are a lot of unconscious processes going on in our brains all the time.
Let me start with your own description for the word “tip”, which you describe as as an impression, which would be a picture, except that you have aphantasia. My experience might be similar (or not), except that I would describe tiny motions, such as the slight tilt of my head to one side when I read the text asking for an explanation of what went on in my mind as I thought of the meaning of “tip”. I became much more aware of the role of small muscular contractions in my thinking when I first became aware that I had no mind’s eye, about 35 years ago. I learned that, if I wanted to stay quiet, it was a good idea for me to sit on my hands. No hand motion, fewer words…but that may just be me. You may not experience anything like that at all.
Then, since the right side of my computer screen showed a hat for sale (Aphantasia Merch!), I thought of the phrase, “to tip one’s hat” which has both literal and figurative meanings. Associated with that came the sense of what it would be like to lift my hand to grasp the brim of a hat.
And then, I thought about tip jars next to registers, and I wondered about why “tipping” means adding something extra to payment for service. No images, and no muscle movements either, for that one. Just a sense of where tip jars are generally located in commercial establishments, as well as where you add a tip on a credit card slip. So this last meaning was mostly associated with spatial relationships.
My guess is that all of these impressions or even visualizations come after the mind has already accessed the meaning of the word, and that those manifestations are just a possible means of bringing that into consciousness, for words that are amenable to that kind of process.
How would you manifest a more conceptual word, such as “inconceivable”? What would a visualization or impression even be? But I know the meaning of the word, and you probably do as well. So there have to be other processes involved in accessing the meanings of words, even if we aren’t conscious of them.