When a person is having a masturbation session, they are about to blow their load, but they haven't got something to unload into, they pick up a dirty sock and blow the load into it. They forget it's lying there for weeks, and the cum makes the sock harden like cardboard.
Tom: Dude, what is up with that smelly sock?

Jeffrey: Dude, I was lazy, I blew my big load into that sock last week and it's like cardboard now.

Tom: Cardboard socks!
by PulsarIrish October 27, 2007
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(n) A Forgotten or misplaced aid for mopping up of excess semen after masturbation / wanking / 5 knuckle shuffle.

Usually under bed for sometime leaving thick, hard casing around item.

"Watched that Roco Sex trainer IX last night...blew up good stlye...
Luckily I found a cardboard sock from last time under the bed"
by Zig Ziggy Treat Teeth April 16, 2009
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