Little known slang term for toilet paper usually of the softer variety. Comes from the fact that Gandalf from Lord of the Rings has a long white fluffy beard.
The public toilet ran out of Gandalf the White!
If during oral sex you ejaculate into you partner's mouth and they spit the cum onto your chin.
I totally gave him the Cumming of Gandalf the White! That's what he gets for cumming in my mouth!