To tweak means to make small, careful adjustments to improve something. When you tweak the settings on your bike's gears to make shifting smoother, or when a programmer tweaks a few lines of code to fix a bug, you're making minor changes that can have a noticeable effect.

The word suggests precision and attention to detail. You don't tweak something by making dramatic changes; you fiddle with it thoughtfully, testing and adjusting until it works just right. A chef might tweak a recipe by adding a pinch more salt, or a musician might tweak the tuning of their guitar. These small modifications often make the difference between something that's merely good and something that's excellent.

Tweaking is about refinement. When your science fair project is nearly finished, you might spend time tweaking the display board layout or adjusting your presentation. The core work is done, but these final tweaks polish everything.

The word can also mean to pinch and pull something, like tweaking someone's nose, though this meaning is less common. When you hear someone say they need to tweak something, they usually mean making those final, fine-tuned improvements that transform good work into great work.