The over-used phrase that ditzy teenage girls use to talk about a "super fun night" or "hilarioussssss pictureeee", not realizing that it makes them sound like they have 8 brain cells. Oftentimes, it's combined with other words to make phrases such as, 'BEST.PICTURE.EVER.' Also, 'BEST.NIGHT.EVER" can be seen and/or heard quite frequently.
Can be mistaken for 'BEST EVERRRRR' which is essentially the same thing, just a more obnoxious and emphatic version.
High school girl sees a picture of herself drunkenly posing with her friends on Facebook: "hahaha omg! best.EVER."
The most true and stripped down raw level of perfection achievable, in any situation attainable. Can be achieved by the satisfaction of contentment in a particular moment.
Hey dude, did you see Rachel the other night? Holy shit, if there was ever a girl that was besteverness, it's fuckin' her man, make no mistake! She is HOT!