To clasp, grasp, or grip something — holding it firmly in one's hand.
転びそうになって、手すりをしっかり握った。
I almost fell, so I grabbed the handrail firmly.
彼はペンを握ってサインをした。
He gripped the pen and signed.
寒くて手をこすりながらカップを握った。
It was cold, and I held the cup while rubbing my hands.
To hold the key or crucial information — to have the answer, advantage, or control in a situation.
彼は決定的な証拠を握っているらしい。
It seems he holds decisive evidence.
ここを押さえれば交渉を有利に握れる。
If we secure this point, we can hold the advantage in negotiations.
To seize or hold power — to control authority or the reins of leadership.
新党が与党の地位を握ることは容易ではない。
It's not easy for the new party to seize the position of the ruling party.
軍が政権を握ったあとは政策が一変した。
After the military seized power, policies changed drastically.
To form or shape something with one's hands (e.g., to press and shape rice for nigirizushi); to mold by hand.
寿司職人が巧みにシャリを握るのを見た。
I watched a sushi chef skillfully shape the rice balls.
子どもが砂場で砂を握って遊んでいる。
A child is playing by grabbing sand in the sandbox.