It has adopted what is known as a “limited-duration shareholder rights plan”, also known as a “poison pill.”

The move will prevent anyone from having more than a 15% stake in the company.

It does this by allowing others to buy additional shares at a discount.

The Twitter board detailed its defense plan to the US Securities and Exchange Commission and put out a statement saying it was needed because of Mr Musk’s “unsolicited, non-binding proposal to acquire Twitter.”

A takeover bid is considered hostile when one company tries to acquire another against the wishes of that company’s management – in Twitter’s case, its executive board.