I keep a running list of new, descriptive, or high-impact words I can use in my writing and presentations. My latest addition is “punditocracy.” What a great word!
The problem I want to solve is that these words and their definitions are in a long Apple Note. I find it hard to review the list consistently.
Is there an app in which I could enter this information that would bring up one of the words each day at a predetermined time? And that does not require a subscription? 
Anki meets your criteria, but is probably more than you need capability-wise. It’s a powerful app that requires some fiddling to get right. The Mac version is free; the iOS is a one-time fee, and not a small one. “Anki” means memory in Japanese. A number of copycat (?) apps have latched onto this name, so be mindful of checking out the correct one, which I’ve linked to.
Anki +1. You could also sort this out with Keyboard Maestro without too much trouble.
The Vocabulary View, Vocabulary Cards, and Spaced Repetition plugins for Obsidian might be worth a look, especially if you already have Obsidian installed.
Another vote for Anki. If I recall correctly, and admittedly it has been some years since I used the app, the web interface on iOS is serviceable if your needs are basic and you want to stick with free.
The category of apps I’d search for is spaced repetition apps. Quizlet is another popular app in this category, although I have no first hand experience of it.
Thanks everyone for the good input. After reviewing options, I decide on Quizlet. Thanks again, much appreciated!