When children who have recently acquired a younger sibling feel so excluded that they pretend the new member of the family simply doesn't exist.
Mary: "Who is that?" (motions to John's younger sibling)
John: "What are you talking about? I don't see anything."
Mary: "Oh John, I forgot you are still suffering from new sibling syndrome."
by yepyepyepyepyepyepyep February 2, 2014
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when you meet someone, who you get along with great, and you find out that you have the same names. a very rare coincidence.
usually between a guy and a girl who share names, (like sam, page, eric, jordan etc...)
person 1: man i've really been enjoying talking to you, but you still haven't told me your name.
person 2: ohh its sam.
person1: MINE TOO!!
person 2: you are totally my New Sibling!!!
by justin blue cheese December 19, 2008
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