眉头 (méitóu) means "brow" or "the space between the eyebrows." It is often used figuratively in expressions related to worry, thought, or displeasure. Common collocations include 皱眉头 (to furrow one's brow) and 眉头紧锁 (brows tightly knit).
他紧锁眉头,一言不发地坐在那里。
tā jǐn suǒ méitóu, yī yán bù fā de zuò zài nàlǐ.
He sat there with his brows tightly knitted, not saying a word.
看到这道难题,她不自觉地皱了皱眉头。
kàn dào zhè dào nántí, tā bù zìjué de zhòu le zhòu méitóu.
Seeing this difficult problem, she unconsciously furrowed her brows slightly.
他的眉头终于舒展开来,露出了笑容。
tā de méitóu zhōngyú shūzhǎn kāilái, lùchū le xiàoróng.
His brows finally relaxed, and a smile appeared on his face.