Tweak

[Couch Potatoe]

To improve. To modify so it runs better, faster, and more efficiently.

[Mark Zuckerberg]

to make a fine adjustment

[Little_Girl]

To be Up and Fidgity From doing Crystal Meth.

[Mark Zuckerberg]

1. to be stimulated by consuming high amounts of caffeine or sugar.
2. to use amphetamine or methamphetamine.

[Britney]

tweak n., slang - Methamphetamine.
tweaker n., - someone high on methamphetamine.
tweak -ing, -ed, v., slang - 1) to be high on methamphetamine,
2) to fine tune.
3) to act as if being high on meth.
4) to pay extended amplified attention to tasks, usually of a trivial nature; especially when other tasks of a larger priority should be handled (with or without the aid of methamphetamine).

[Justin Bieber]

To injure slightly, to sustain a slight injury to (some part of the body), usually while playing a sport.

[Tanya Shivari]

To flip out

[Rihanna]

To pinch and pull with a sudden jerk and twist; to
twitch; as, to tweak the nose.

[Becky]

When you modify a certain piece of hardware for better performance, it is often referred to as tweaking it. Overclocking the computers CPU or changing jumper settings on the motherboard are common examples of hardware tweaking. Removing system limitations and adding plug-ins or extensions to a computers operating system are types of software tweaking.
Tweaking a computer is much like tuning a car (you know, the ones with the huge mufflers, big spoilers, and pimped out rims). It may increase performance, but is best left in the hands of the technically savvy. For example, overclocking your computers processor may cause it to crash frequently, or worse yet, overheat and destroy the CPU. So, for most people, it is best to leave well enough alone.

[Jessica]

Twist or pull (something) sharply.