"Wiggly crochet" is a surface crochet technique, meaning that you crochet onto the surface of a fabric to get the desired effect. There are various other surface crochet techniques; with this particular technique, people typically crochet onto a mesh worked using double crochet and chain stitches. The mesh might be the same sort of mesh you'd make for filet crochet, except without any filled-in blocks. In some cases people prefer to work the mesh in the round. The mesh itself is hidden when the surface crochet is applied to it, so the effect is vastly different from the effect achieved in filet crochet.
There are other possibilities as well, and you will see some interesting variations if you peruse the pattern links posted below.
This technique tends to result in fabric that is dense, heavy and not-at-all "drapey." It's good for making projects such as hot pads, rugs, bags and pillows.
The following links will help you get a clearer understanding of this technique, how to do it, and what you can make with it.
Free Wiggly Crochet Tutorials and Patterns at the K-Town Blog
Barbara Langer has posted several items of interest on the topic of wiggly crochet:
This set is bright, cheerful and pretty! This easy pattern was designed by Susan Lowman, and it is posted on the Coats and Clark website.
These potholders might or might not be vintage, but they sure do remind me of a vintage look.
This tutorial is posted at the "Nonna Luna" blog.
These retro-inspired potholders are colorful and fun. The free patterns include symbol crochet charts. You'll find the free patterns posted at the Crochet Today website.
This solid-colored hotpad is pleasantly textured. The free pattern is posted at the crochetnmore website.
Here's something a little different; it's a kid-friendly wiggly crochet hat pattern. It's posted at the "crochet me crazy" blog.
This baby blanket features bunches of "wiggles" crocheted in colorful wiggly stripes.
Here's a pattern for a cute granny square with "wigglies" all over the surface of it.
Yet another multicolored wiggly crochet hotpad. This one is posted at the Angelfire website. You may have to close a popup to see the free pattern.