A Cross of Peter is an inverted Latin cross
The Cross of St. Peter or Petrine Cross is an inverted Latin cross traditionally used as a Christian symbol, but in recent times also used as an anti-Christian symbol (a meaning different from that of traditional Christian symbolism).
The origin of the symbol comes from the Catholic tradition that Simon Peter was crucified upside down, as told by Origen of Alexandria. The tradition first appears in the "Martyrdom of Peter", a fragmented text found in, but possibly predating, the apocryphal Acts of Peter, which was written no later than 200 A.D. It is believed that Peter requested this form of crucifixion as he felt he was unworthy to be crucified in the same manner that Jesus died. As such, some Catholics use this cross as a symbol of humility and unworthiness in comparison to Jesus.
According to Roman Catholicism, the pope is Peter's successor as Bishop of Rome. Therefore the Papacy is often represented by symbols that are also used to represent Peter — one example being the Keys of Heaven, another the Petrine Cross.
The Cross of St. Peter has sometimes become associated with anti-religious imagery, as it is used to represent the opposite of Christianity by inverting its primary symbol, the Latin Cross. As a result, the symbol has become popular within anti-religion groups.
It is also a recurring motif in punk rock and heavy metal, where it is embraced as symbol of anti-authoritarianism and defiance (but not necessarily Anti-Christian), and is featured in the iconography