I thought of this answer, then proceeded to try alternatives for 10 minutes since I didn't think it could possibly be right. My mistake! I think my earlier guesses of 'vixen' or 'fiend' were better options for #500.
Really dumb one today. I had it typed in for number 3 but thought surely no. And decided to play a more common letter assuming I wasn't on the right track at all. And then guess #4 was just spite because it was more of a word, but I should have sucked it up and stuck with the rules of the game.
Plural? Fuck you!
Conjugated verb? Fuck you too!
Adjective form? Hell yes! We love adjectives! Even if they're made-up sounding adjectives that nobody actually uses! Just slap a Y on the end of anything. It's fucking magic-y.