a person who is like family but not blood related, someone who you are so close with you basically are family, a
family friend.. it
saves alot of time instead of having to explain that your
not really realated but just very close
your moms best
freind from high school you see every weekend is like your costco
aunt or if you have someone you see alot around your age but your not that close they are your costco
cousin you would say "this weekend im going to me my costco cousin" instead of "this weekend im going to visit this girl whos like my cousin but not really were just very close"