While many people, such as Laurels and those concerned with authenticity, strive to create authentic medieval garb and other crafts, much of the material culture that makes up the SCA could be considered medievaloid.
Dresses bought in a fantasy or renaissance faire store are usually medievaloid - they look medieval to the untrained eye but don't quite fit any one time, place or style. Other examples would be leather belts with a metal loop instead of a buckle, heraldic banners with modern symmetry, and the concept of everyone at a feast having a knife as the only utensil and drinking from pewter beer steins.
In most cases, especially for beginners, medievaloid fits under the category of "best effort" and passes all but the most critical scrutiny. Where the line is between medievaloid and "just tacky" is hotly debated.