What is an inoffensive or indirect expression substituted for one that is offensive or too harsh?

An inoffensive or indirect expression substituted for one that is offensive or too harsh is called a "euphemism." Euphemisms are often used to soften the impact of difficult or unpleasant topics, such as saying "passed away" instead of "died." They help to convey sensitive subjects in a more gentle or palatable manner, allowing for more tactful communication.