A combination of "significant other" and "friends." First known use on June 24, 2011 by howaboutwe... writer Scott Alden.
1. A close friend who appears to be a significant other to those who do not know the subjects.
2. A friend with whom you do not have sex or date, but whoever you do have sex with or date is unwarrantably jealous of.
1. A: "Are those two dating?"
B: "No, they're just significant frothers."
2. Steve dumped Julie because he always got jealous when she would mention her significant frother.