Basically, in a lot of fandoms, there are things called “shippings" (short for "relationships"), which are romantic pairings between (usually) fictional characters. They can range from canon (affirmed in the actual series) to crack (COMPLETELY WTF pairings that have no evidence and would never actually happen). Shippings usually play a HUGE role in fandoms.So, if someone uses the pickup line "I ship us", s/he means that they support you and him/her as a romantic couple.Hopefully that answers your question!
what does the pickup line "i ship us" mean? hahah