This is really hard without a picture. Busto is I imagine a corset and they usually were V shaped. so maybe this is talking about the edges. The ones with tooth like edges are called "tabbed corsets". Google the term and you will find pictures.

see
https://www.britannica.com/topic/hoop-skirt#ref110464
https://www.britannica.com/topic/dress-clothing#ref168815
In contrast, the skirt was shaped into a cone or inverted-V silhouette by being draped over a petticoat made from canvas and inset at intervals with circular hoops of wicker.

but some have zig-zag hemlines such as these:
https://www.pinterest.com/pin/170151692144598300/
https://www.amazon.com/Renaissance-Corset-Elizabethan-Versio...