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1.
two of the most prestigious greek letters. shared my the frat Phi Beta Sigma (1914) and Zeta Phi Beta (1920). This letters symbolize the only TRUE brother and sister organiztions in the National Pan-Hellenic Council.
"PHI BETA" its all one family.
by Jasmine taylor August 30, 2007
 
2.
A widely used term by college students (particularly frats) to describe a massive slut and or bitch (Phi=fucking Beta=Bich)
"Dude that chick Catlin is a huge Phi Beta"
by Andrew Piccirillo July 19, 2006