The (International Protection Rating or Ingress Protection Rating) is defined by international standard IEC 60529 . It classifies the levels of protection against the intrusion of solid objects (dust, sand, debris) and liquids (water). "IP" stands for Ingress Protection.
When selecting an RF connector, it is important to consider the limitations of board space vs. signal performance: Connector Type Typical Application Signal Integrity Robustness Tiny board-level connection IPX-822 Pigtail Board-to-antenna bridging Excellent High SMA External Antenna Interface IPX-822