The term "smudge" has multiple meanings depending on its context.
1) In a general sense, smudging refers to an act or process of blurring or obscuring something, making it unclear or indistinct. For example, one might say that the artist's brushstrokes were so subtle and delicate that they managed to "smudge" the lines between colors in her painting.
2) In a more specific sense, smudging refers to a traditional Native American practice of burning certain herbs (such as sage or cedar) for spiritual purposes, such as cleansing a space or person from negative energy or influences. During this process, the smoke produced by the burning herb is used to "smudge" an area or object, hence the name of the practice.
3) In yet another context, smudging refers to the act of altering or obscuring text in a document, usually for the purpose of hiding sensitive information from unauthorized individuals. This type of smudging is often done using software tools designed specifically for this task.