A person with no idea how to use any kind of technology. The joke is, all digital clocks, stereos, DVD players, VCRs and so on have their displays flashing 0:00 or 12:00 (twelve o'clock) because the person in question has no idea how to set the time, let alone use any other function offered.
{When standing behind someone at an ATM for a very long time} - What is taking him so long? He must be a twelve o'clock flasher..
I knew i was dealing with a twelve o'clock flasher when she put the CD in data side up.
Can you believe it?! He was trying to use his DVD-ROM to read a floppy! Bloody twelve o'clock flashers!
Flashing or showing your tits (if female) or genitals (male or female) to one or more persons with the intent of attracting their attention and creating a sexual response.
Carla got laid repeatedly over summer break. She just went to the beach and flashed credentials.