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."