The sudden boost of winrate or BB/100 when your running hot at online poker.
Also related to the phenomenon of winning excessively after signing up a new account at a online poker site.
Can also be used as adjective to define running good at all forms of life.
The inverse of doomswitch.
My boomswitch just flipped on at Stars, I am up 10K today!
I just signed up at Party and they gave me a boomswitch account, I can't lose.
Dude, I got boomswitched at the bar lastnight, 5 birds numbers in and hour.