A term which refers to a woman's figure in such a condescending way that not one woman has yet been found to appreciate the phrase. "Fit rig" refers only to women who do indeed have a BMI in the dangerously underweight range and keep themselves in what those in the fashion industry would could consider good shape. This term is used almost solely in an all-male domain.
Gazza: "Hey Watto, check out Gemma. I don't reckon she's eaten in 6 weeks"
Watto: "I know aye, she got a fit rig!"