I've seen this term used before and just saw it again when I looked at the International school of sugarcraft books....Can someone explain it or post a picture??? THANKS!!!
I googled Define Bas Relief & heres what I came up with:
http://www.google.com/search?hl=en&lr=&defl=en&q=define:bas+relief&sa=X&oi=glossary_definition&ct=title
I hope this helps 
Bas Relief is one of my favorite art forms in sugarcraft. It is sculptural and is the use of padding under sugarpaste to achieve a three-dimensional effect. It's NOT 3D but the image is raised above the cake. You have definte highs, lows, highlights, lowlights and shadows achieved.
The kissing couple cake below is made usung a bas relief technique. Both the little girl and little boy are padded and are raised from the cake top. The boy's hand is raised above his body and has space to hold a 3D detachable bouquet of flowers.
If you are interested to learn further, there is a great book called "Bas Relief & Applique" by Lesley Herbert that you might want to review.
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