noun
Refers to an amount that can be held in one hand, often used with の to modify a noun.
彼は一掴みの砂を拾った。
He picked up a handful of sand.
noun
grasping (with one hand); grabbing; taking a handful
The action of seizing or scooping something with one hand; often used in the phrase 一掴みにする.
彼は髪を一掴みにして引っ張った。
He grabbed a handful of her hair and pulled.
一握り also means 'a handful', but it emphasizes the amount that fits in a closed fist, while 一掴み focuses on the act of grabbing or the amount scooped up with fingers.
Compound of 一 (ひと, 'one') + 掴み (つかみ, 'grasp', the noun form of 掴む 'to grab').