If 4+ is a save, and 4++ is an invuln, and 4+++ is a Feel No Pain, what's a shroud?

What ARE general threads? Can we put together a working definition of one for internal use?

Obviously we all "basically" know what a general thread is but I'd like a concrete definition that we can use as a basis for further dicussion.

Side discussion: please offer your thoughts on general threads both within the boards you use the most, and in general.