/ skʌl; NAmE / noun
1.
the bone structure that forms the head and surrounds and protects the brain
SYN cranium :
a fractured skull
—picture at skeleton
2.
( informal ) the head or the brain :
Her skull was crammed with too many thoughts.
( informal )
When will he get it into his thick skull that I never want to see him again!
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WORD ORIGIN
Middle English scolle ; of unknown origin; compare with Old Norse skoltr .