This Makes Me As An Amumu Main Cry A Little
For those not in the loop, 'disarms' are abilities that remove a player's ability to basic attack. While most cc does this (because you can't move period), Lulu's Whimsy and Amumu's Curse of the Sad Mummy are unique in that they either let you still move (in Lulu's case), or they let you cast spells (in Amumu's).
So we're calling them disarms. And now they're affected by Tenacity. The following abilities are affected by Tenacity:
Amumu R - Curse of the Sad Mummy Lulu W - Whimsy
http://static2.gamespot.com/uploads/scale_super/1551/15516851/2941764-lfs13.png