Grip, Handle, Handful, Fistful
noun
Remember how 握る is "to grasp"? This is the noun version, making it a grip.
にぎり
The reading comes from 握る, so get a grip on that!
怒ったコウイチは、握り拳で机をバンバン叩いた。
Angry Koichi banged on the desk with his clenched fists.