EBay on Tuesday rejected GameStop 's $56 billion takeover proposal, calling the unsolicited bid "neither credible nor attractive."

GameStop CEO Ryan Cohen last week unveiled an audacious bid for eBay, offering to acquire the online marketplace for $125 per share in a cash-and-stock deal. EBay is much larger than the video game retailer, with a market cap of just over $48 billion, while GameStop's is roughly $10.3 billion.

"The Board, with the support of its independent advisors, has thoroughly reviewed your proposal and has determined to reject it," Paul Pressler, the chairman of eBay's board, wrote in a letter .…