https://www.siliconvalley.com/2022/04/15/twitter-adopts-poison-pill-defense-in-musk-takeover-bid/

PROVIDENCE, R.I. (AP) — Twitter said Friday that its board of directors has unanimously adopted a “poison pill” defense in response to Tesla CEO Elon Musk’s proposal to buy the company and take it private.

Twitter said the move, formally called a “limited duration shareholder rights plan,” aims to enable its investors to “realize the full value of their investment” by reducing the likelihood that any one person can gain control of the company without either paying shareholders a premium or giving the board more time. Poison pills are often used to defend against hostile takeovers.