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1. MSB
Abbreviation for "massive sperm buildup", often incurred after a long sexual drought; common malady among geeks
<dumpee> duder, ever since she left me, I've had some serious MSB going on
by grasshoppers Jan 20, 2003 add a video
2. msb
middle school bitch. one that wears excessive amounts of abercrombie apparel, attains a facebook around age 12, and always seems to have a new series of naked pictures out. Identifying an msb: prefers to straighten her hair, owns some sort of coach bag, says things like "loves it" and AlTeRnAtEs CaPiTaLiZiNg LeTtErS wHeN sHe tYpEs. like so (the written msb language also often includes numerous asterisks, hearts, and exclamation points.) <33 :)

"That msb sent me pics last night, so I sent 'em to everyone I know."
3. MSB
Stands for Mother Sister Black. A woman that is african-american, has children and is known to a guy as his buddy's sister would classify as an MSB. Most white men have an 'achivement sex list' which includes a mom, a black girl, somebody's sister, a teacher, etc... If a white guy has sex with an MSB it is considered a powerful achievement.
Duder 1: "I can't believe you fucked Garrett's sister. She's half black and has a kid dude. You totally scored an MSB!"

Duder 2: "I know man, it was pretty amazing. Those titties were so nice."

Duder 1: "Damn! You're so far ahead of me now. All you have left on your list is a teacher. I got a lot of catching up to do."
4. MSB
Mother Sons of Bitches; person or persons placing constraints on actions of others; "The Man"
Persons are not permitted on the boat canopy, by order of the MSB
5. MSB
short for 'Massive Sperm Buildup' - usually occours in young male adults under 25 as a result of no sexual activity for more than a week or 2
Derek had not masturbated for about 3 weeks and was suffering from a severe case of MSB, but after watching 5 minutes of crazy cumshots #4 he had a massive sperm bomb and had to use his blue bandanna to clean up!
6. msb
A Acronym derived on the MMORPG "Runescape" First used by a player known as Staple,or "Nibo." It means (M)ad (S)ad (B)ad as a flame toward raging players that are considered "Bad" at the game.
l0l why you so msb bro?!
7. msb
(noun) 1. my sexy bitch
person1:hey msb;)
person2:msb?
person1: yeah, you're my sexy bitch
person2:oh.. okay then:P
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