scrunch up is a verb meaning "sit on one's heels". It carries 2 recorded senses.
make wrinkles or creases on a smooth surface; make a pressed, folded or wrinkled line in; `crisp' is archaic
“The dress got wrinkled”
“crease the paper like this to make a crane”
archaism
Definitions, synonyms and semantic relations for scrunch up come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.