One informal method that has been used to change the meaning of the constitution is the loose interpretation argument made by President Thomas Jefferson when buying the Lousiana territory from France.
When Jefferson was president at the beginning of the 19th century, there were still questions on what rights the president possessed. This was especially true when it came to making deals with foreign countries. Even though Jefferson did not like the idea of a loose interpretation of the constitution, he used it during his presidency. A loose interpertation of the constitution essentially states that just because a right is not given to a president explicitally in the constitution, it does not mean that the right doesn't exist. This is why Jefferson went on to purchase the Louisana territory from France, nearly doubling the size of the United States.
This event changed the interpretation of the US Constitution, as future presidents saw it as acceptable to buy land from foreign countries. There were multiple examples of this during the era of westward expansion in American history.