What is this type of hairstyle called?

I'm looking for the name/picture of a hairstyle that is a bit difficult to describe. I've only seen it on actresses in movies, but I unfortunately can't recall any specific actresses or movies. The style has all of the hair up in what I can only describe as a bun in the back. The "bun" is rolled inwards into itself, and there are no visible clips/ties/etc. I know this is vague, but I'm having a terrible time trying to find or describe it. Thank you for your help!