When someone says, "don't even think about it," they are using a phrase to strongly discourage or prohibit a particular action or behavior. It is often said in a stern or assertive tone to emphasize the seriousness of their statement.
Essentially, the person is telling you not to consider or entertain the idea of doing something they find unacceptable, undesirable, or inappropriate. It serves as a clear warning that the action in question is not to be pursued or even contemplated.
For example, if a friend says, "Don't even think about eating the last piece of cake; it's for someone else," they are firmly telling you not to consider taking that action. It's a way of setting a boundary and letting you know that the action is off-limits.