An amendment to a corporate charter making it more difficult to repeal amendments that have previously passed. A lock-in amendment is usually used as an anti-takeover measure. For example, a company may pass a lock-in amendment stating that a previous anti-takeover amendment to the charter requires a 75% majority of shareholders to be repealed.
Amendment to a corporate charter that makes it more difficult to void previously approved amendments. For example, a lock-in amendment may require 60% approval to change an existing antitakeover amendment.