Answer: sigep

AnswerCrossword Clue
SIGEPLargest college fraternity in the U.S., in brief
SIGEPColl. fraternity with a skull-and-crossbones symbol
SIGEPMember of a popular college frat
SIGEPPopular fraternity, familiarly
SIGEPCollege frat with the greatest number of chapter houses (200+)
SIGEPFirst college frat to charter a chapter in all 50 states
SIGEPLargest frat in the U.S.