/frob'ni-kayt/ (Possibly from frobnitz, and usually abbreviated to frob, but “frobnicate” is recognised as the official full form).
To manipulate or adjust, to tweak.
One frequently frobnicates bits or other 2-state devices. Thus: “Please frob the light switch” (that is, flip it), but also “Stop frobnicating that clasp; you'll break it”. One also sees the construction “to frob a frob”.
Usage: frob, twiddle, and tweak sometimes connote points long a continuum. “Frob” connotes aimless manipulation; “twiddle” connotes gross manipulation, often a coarse search for a proper setting; “tweak” connotes fine-tuning. If someone is turning a knob on an oscilloscope, then if he's carefully adjusting it, he is probably tweaking it; if he is just turning it but looking at the screen, he is probably twiddling it; but if he's just doing it because turning a knob is fun, he's frobnicating it.