tweaker

Etymology

 * the drug-addict sense comes from the nickname for methamphetamines, in reference to addicts' punding behaviour.

Noun

 * 1) A person who tweaks something.
 * 2) A tool, especially a screwdriver, for making small adjustments.
 * 3)  A person addicted to methamphetamine.
 * 4)  A spin bowler.