I decided to start a new question because I have no idea what word describes it at best, let alone to do a research (aka googling) which can be a bit inconclusive.
At first glance, it looks like it convincingly represents an LED, albeit not with the proper LED symbol (there is a diode symbol at the bottom, which makes sense.) Also the epoxy lens/dome and the die. Yup, it is closely modeled after a classical 3mm/5mm LED light.
Well, here comes the doubt. This symbol is often found on analog volt meters. (I found mine in an automatic voltage regulator) but I'm sure that this symbol might be around on other devices. Interestingly enough, the devices that bear this symbol often don't directly involve any LEDs besides indicator lights (the AVR in the picture doesn't even have one.)
What does this symbol mean?