Middle Child Syndrome (mid-l chahyld sin-drohm]: noun, a son or daughter displaying a group of symptoms (feelings of unfairness, dramatics, extreme stubbornness, abundant creativity, swings between confidence and self-loathing, humorous, quick on the uptake, occasional crazy eyes) characteristic of the disorder of being born between two or more siblings. (Note: while popular opinion associates this disorder with low self-esteem, many with middle child syndrome vehemently disagree. And if one continues to insist on such connotations, the middle child will show you just how confident he really is. The author of this entry highly recommends that you duck. Now.)
Example #1: “Yeah, he’s batshit. He can’t help it; he’s got a wicked case of middle child syndrome.”
Example #2: “I’m so proud! My oldest is a doctor, my youngest just got married, and my other one…well, she’s still alive.”
Example #3: “FUCK YOU! DON’T TOUCH MY STUFF!”
The Dictionary of Cari, created because Webster’s doesn’t always get it quite right.