Dragons' Den is the UK business reality show in which a Dragon signals rejection by saying “I'm out.”
The phrase is part of the programme's recognizable investment vocabulary. Entrepreneurs present a proposal, state how much money they want and explain what share of the company they are prepared to offer. A Dragon can ask questions, make an alternative proposal or leave the negotiation by declaring that they are out.
The wording does not mean the entrepreneur has necessarily failed in every respect. It means only that the particular Dragon will not continue pursuing that pitch. Other investors may remain interested, and a deal shown on television can still be subject to due diligence and later contract discussions. The expression has become closely associated with Dragons' Den, although the broader idea of investors withdrawing from a negotiation appears in many business programmes and adaptations of the format.