1. To change slightly, usually in reference to a value. Also used synonymously with twiddle. If a program is almost correct, rather than figure out the precise problem you might just keep tweaking it until it works. See frobnicate and fudge factor; also see shotgun debugging.
2. To tune or bum a program; preferred usage in the UK.
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Nearby terms: tv « tw « TWAIN « tweak » tweening » tweeter » TWENEX