Light-switch romance (compound noun, singular)
An intense on- and off-again romantic relationship between two people. It’s an analogy to the on/off button of a light-switch interrupter. There’s no in-between. It’s either full on or full off.
Notes: Naturally, this doesn’t take into consideration the use of a dimmer for the light-switch. I just had to say that because I found that funny.
Ex: Regina’s light-switch romance with her biker boyfriend recently got out of hand.