A transparent panel or yoke attached to the bodice that extends from the bust to the collar; constructed of tulle, net, or lace.
Termwiki
Let’s take a look at some of the illusions the royals have offered to us.
Queen Maxima wore this Jan Taminaiu gown for the stunning debut of the full Stuart tiara during the state visit to Britain. This is a cape over a strapless gown, but the illusion effect is in full force and I’m calling it for this category.
Sofia Hellqvist as-she-was wore an Ida Sjöstedt illusion neck gown to her first Nobel ceremony in 2014.
Crown Princess Victoria (and Oscar) appeared at the 2015 Nobel ceremonies in a burgundy gown with an illusion neckline.
Crown Princess Mary shows us the sparkly illusion.
It’s a challenge, I know. This is not your everyday neckline – but I know the Baguettes can find some excellent examples! If you need to expand the category to “illusion effect” – as I did for my first example up there – throw it out there for discussion ; ).