a gradual transition into the realms of trisomy 21 usually occuring after adolesence
symptoms include:
a gradual lowering of the i.q.
tounge lolling
compulsive masturbation
"Lily is getting dumber by the second, maybe she has adult onset downs (A.O.D.)"
by Andrew LanDOWNS September 1, 2008
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When parents are trying to call their teenagers to tell them that it is time to come home and the teenager for some apparent reason does hear the cell phone ring so that they can stay out longer with their friends.
While trying to call my son to tell him that he is out past his curfew and needs to come home, he contracted

Cell-U-Lar Onset Deafness, and does not hear the phone call from his mom.
by peaceangel22 June 27, 2011
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An extremely technical and euphemastic way of saying getting shot with a gun.
The man walking down the street alone at night in Chicago suddenly had a terrible case of Rapid Acute Onset Lead Poisoning and died right then and there.
by Robjef622 May 8, 2017
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When someone, through some means (usually weight loss), gains a large and sudden boost to their confidence that turns them into egotistical dickheads. It can also exacerbate egos for people who were faking it and now that they have real confidence it makes them appear like they're bragging all the time.
Fella: Hey, did you see that Gary lost a ton of weight recently?
Mate: Yeah! Notice how he hates fat people now? And he scoffs at chicks that he previously would have crawled dick first through a valley of glass just for them to notice him?
Fella: I have!

Mate: Ya boy's got a bad case of Sudden Onset Confidence Syndrome.
by RussNuts July 16, 2019
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Sudden Onset Defecation or S.O.d. which is difference between let’s stop at the next rest stop and PleasePullOverNow!
“Damn Ron, what took you so long?”
“Well Dave, I had an emergency Sudden Onset Defecation and barely made it to a WaWa.”
“Oh I understand that. I had a SOD last week and I’m not allowed in Walmart anymore.”
by Saloondoor June 30, 2023
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An instrumental song by the Japanese hard rock band, Band-Maid.
They should've given Akane a longer solo, but the main focus of Onset is, of course, Her Shreddiness, Kanami.
by TeaN'All February 4, 2020
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When all your friends turn into douchebags when they were once nice. It's real.
"Don't be a sod."

Billy: Hey dude, wanna go to the movies today?
Todd: No dude I got in with the wrong crowd, now I have sudden onset douchebag syndrome.
by Toddthedouche January 12, 2011
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