(ˈ)fu̇l, |fəl+ noun
Etymology: Latin ful gur lightning (from fulgēre to shine, flash) + English chronograph
: a lightning-recording device that consists of a revolving aluminum disk having on its rim several hundred steel fins which, as they pass successively every forty-millionth of a second between two coils carrying the surge current of a lightning stroke, become proportionately magnetized and register the duration and intensity of the strokes