A poison pill is a defense tactic used by companies that are targets of hostile takeovers that gives existing shareholders the right to buy additional stock at a discount, thereby diluting outstanding stock.

Following the blockbuster news Tuesday, April 14 that Musk has offered to acquire Twitter for a premium of $54.20 a share in cash, Twitter called an emergency meeting of the board of directors for 10 a.m. Pacfic (2 p.m. EST) and an all-hands meeting for 2 p.m. Pacific (5 p.m. EST).

Musk said he has "sufficient" funds to make the purchase outright. He has also said that he has a "Plan B," without specifying what that plan is.

Musk also said Thursday he made an offer to buy Twitter because he believes "it's very important for there to be an inclusive arena for free speech."

In an interview at the TED Conference in Vancouver, Musk said he believes Twitter's algorithm should be open-source and suggested the code behind Twitter should be available on Github, a Microsoft-owned platform for sharing code for software development.

"Having a public platform that is massively trusted, and broadly inclusive is extremely important to the future of civilization," Musk said during the interview with Chris Anderson, Ted Conferences curator and a former editor of Wired.