I’ve spent a lot of time trying to clinically classify each Dominion card and there’s a ton of nuance to the word “trash” that can basically only be resolved by deciding beforehand what you want it to mean. Whatever a trasher is, Chapel definitely has to be one, right? But Bandit trashes cards, but you can’t use it on yourself. Remodel trashes cards but you still end up with the same number of cards in your deck. Trader trashes cards but you end up with more cards than before you played it! Which of these is a “trasher” and which is not?
I generally use the terms “thinner” to refer to cards that reduce your deck size and “remodeler” to refer to cards that trash cards but don’t reduce deck size. I save the word “trasher” for trashing attacks like Knights. When I’m being extra-detailed I add “trash-for-benefit” which, for the sake of usefulness, excludes remodelers, and this refers to cards like Moneylender - even though Chapel trashing four coppers out of your deck is technically a benefit.
I’d either call Rats a remodeler or a trash-for-benefit, as it just isn’t helpful enough to call it a “trasher.”
Feel free to disagree, but if anyone has a different classification I’d like to see how you navigated having four different types of cards go by the same moniker.