To grasp or hold something tightly with one's hand so it does not slip or fall.
子供が母の手を握り締めて離さない。
The child grasped his mother's hand tightly and wouldn't let go.
彼は大事な写真を握り締め、目に涙を浮かべた。
He clutched the precious photograph tightly and had tears in his eyes.
寒さで震えながらペンを握り締めてメモを書いた。
Shivering from the cold, he gripped the pen tightly and wrote a note.
逃げる前に彼は封筒を握り締めた。
Before running away, he clutched the envelope tightly.