I'm also not keen on the word 'resistance'. I learned early on that if you hunker down with muscle to prove a point to nage, it is a quick path to getting injured. I've seen it happen all the time....uke starts 'resisting' and nage, because they can't figure anything else out to do, puts all their weight, muscle into achieving the desired end....and ouch...it is all fun and games until someone gets hurt!
(I was at a seminar once and was in a line where a high level yudansha tried to prove a point to a much larger, but less knowledgable white belt....and the yudansha almost lost his arm for his effort. Honestly, it made me laugh because the same white belt had just thrown me...and I could see he was nervous...and I could see he really didn't get the technique...and it wasn't really the place to try to correct him, so I just let him lead me where he would....the yudansha was so mad and came to the back of the line and ask me "did he hurt you too?" I said "No, but I'm just a girl." :~) )
To be honest, I find that varying the speed of the attack (maybe a little faster, maybe a little slower) does wonders for freeing up nage's mind (and muscle). Works a lot better than 'resistance'. And, it makes sure that I'm doing my job as uke...keeping an attack that is true to the technique being taught....