To jab means to poke or thrust something quickly and sharply, usually with a pointed object or your fist. A boxer jabs with a short, fast punch, snapping his arm out and back. You might jab your finger at a calculator button when you're in a hurry, or jab a pencil at a word you want someone to notice.

The motion is quick and direct, not sweeping or slow. When you jab at something, there's a certain sharpness to it: a jab with your elbow to get your friend's attention, or a jab with a stick to test whether something is safe to touch.

A jab can also be a verbal poke at someone. If your brother makes a jab about your messy handwriting, he's making a quick, pointed comment meant to tease or criticize. These verbal jabs aren't usually meant to cause real hurt, but they can still sting a bit, like the physical motion they're named after.

In medicine, people sometimes call a shot or injection a jab, particularly in British English: “I got my flu jab yesterday.”