"crumpling" in the verb sense
1. crumble, crumple, tumble, break down, collapse
fall apart
"the building crumbled after the explosion"
"Negotiations broke down"
2. buckle, crumple
fold or collapse
"His knees buckled"
3. pucker, rumple, cockle, crumple, knit
to gather something into small wrinkles or folds
"She puckered her lips"
4. rumple, crumple, wrinkle, crease, crinkle
become wrinkled or crumpled or creased
"This fabric won't wrinkle"
Source: WordNet® (An amazing lexical database of English)
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