Uncontrollably means in a way that cannot be held in check. Shaking uncontrollably, laughing uncontrollably, weeping uncontrollably.
It belongs to the body above all, since the things done uncontrollably are shaking, laughing and crying. That is what makes it a useful signal in writing, because the person has stopped choosing.
1adverbuncontrollablyIn a way that cannot be held in check.
“The children giggled uncontrollably when the teacher sat on the whoopee cushion.”
uncontrollably is a manner.
From uncontrollable + -ly.
Etymology from Wiktionary, CC BY-SA