pê-thâu-khak扒頭殼

to scratch one's head

to scratch one's head (in handling a difficult matter)

English Wiktionary, “扒頭殼” (CC BY-SA 4.0) — https://en.wiktionary.org/wiki/%E6%89%92%E9%A0%AD%E6%AE%BC · confidence: Medium (Wiktionary)