A giant, slow-growing, epic-ly painful zit. The kind that you can't pop successfully for days even though it resembles a small volcano on your face, because its source is so deep. Often used as part of the phrase "massive underburner."
This term was coined by Alice Thomas in Columbus Ohio, in approximately 1993.
The act of saying unkind, critical, cranky, peevish things about your spouse while both you and your spouse are in the company of others, often as a passive-aggressive way to make a point *to* your spouse about some trait or behavior that you find problematic, in the guise of conversing with others.
Guys, enough bitterspousing already! Let's all have fun tonight!
Jim and Cheryl ruined the evening with their constant bitterspousing.