This word is derived from a misspelling of "Deceiver". It has risen in popularity with the rise and prominence of Facebook's Marketplace.
A Deceder is someone who constantly lowballs people but also lies about market price.
Usually a noun, it can also occasionally be used as an adjective.
I knew my comic was worth $100, and this Deceder guy said he'd give me 70% of value, but then when we met up in person he claimed it was only worth $80, and tried to pay me $56. Just a huge waste of time.
That guy was such a Deceder, you'd think he was from Austin TX, home of the lowball king, and "Following for Price Drop."
To Deck, To get decked; to hit or be hit viciously hard without mercy, usually in the mouth or nose region. To strike down upon another human with great vengeance and FURIOUS anger.
"I just decked Stephanie in the nose cuz the bitch didnt have my money"
"If my manager doesnt give me next friday off ima deck him right in his mouth