a PIP stands for a Pool in pool. an inflatable pool which you put inside your own pool, and you and your friends can just chill in the pip with all of your clothes on. it acts as a boat, but is much more comfortable. Example: lets go pipping. as in, lets do the deed of sitting in a PIP.
PIP
Meaning of PIP in English
Slang English vocab. Английский сленговый словарь. 2012