KanjiJLPT N3
Stab

stab, protruding, thrust, pierce, prick, collision, sudden

Mnemonic

You peer into a hole and spot something big shifting in the darkness below. WHOOSH—a massive horn rockets upward to stab you through the jaw! A big bull was trapped in the hole, and it just gored its way to freedom straight through you.
Additional thoughts
Picture the kanji structure: hole on top, big on the bottom. The big thing is IN the hole, thrusting upward violently. A bull's horn shooting up through a pit is sudden and brutal—matching the kanji's sense of abrupt, forceful piercing.
Quick recall
A big beast in a hole rockets its horn up to stab you.

Details

The keyword for 突 is stab. This kanji conveys the idea of a sudden, forceful thrust or piercing motion, like lunging forward to stab at something. By extension, it also carries the meaning of something happening abruptly or unexpectedly, as in a sudden rush or charge. The sense of violent, pointed contact underlies both its literal meaning of poking or thrusting and its figurative meaning of突然 (suddenness).
On'yomi
とつ、か
Kun'yomi
つ.く