I was also wondering what that term meant..I 'm thinking that it is a stone setting that has no "underpinning " holding it in place...it is just set in place with nothing underneath it, but I'm not sure....maybe someone else has a correct answer.
Lorraine
I think the hole is for light to shine through.it's not called venting it's called a seat. almost all stones have a point on them so when the jeweler has to cut the seat he drilles a hole all the way through the gold so the point has some where to go. and no that is not a hole so the stone can breathe