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When Someone Claims They've Forgotten Something Simply So They Don't Have To Admit Truth/ Guilt BUT It's Blatantly Obvious They DO Know About Said Circumstance.

Also Can Be Used To Withold Information From Someone To Get Your Way.

"I Wasn't There, How Could I Have Been?" (Smirk)
"I Think You Have Shamnesia....." (Questioning Look)

"Can You Remember? Then Neither Can I....." (Arrogant Attitude)
"We'll Have To Push Harder, This One's Conveniently Got Shamnesia...."

"I Could Suddenly Remember What You Want To Know If You insert demand here" (Bargaining)
"I Think She/He/It's Wasting Out Time. I Hate Shamnesia"
by sparkstersfury February 15, 2009
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When you shampoo your hair a second time because you forgot doing the first time.
I use up the shampoo twice as fast because of my chronic shamnesia.
by JetCityJoe December 22, 2009
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When a Phish concert kicks your ass along with the LSD and or MDMA and you've concluded that it was the best thing you've ever heard.
Jordan is suffering from shamnesia after candy flipping at last nights Phish concert.
by japmeatstick July 31, 2017
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