Is calcium oxalate soluble in water?

According to http://www.americanelements.com/caoxl.html , calcium oxalate, $\text{CaC"_2"O"_4}$ is "highly insoluble in water."
No, calcium oxalate, $C a {C}_{2} {O}_{4}$, is not soluble in aqueous solution.
The solubility of calcium oxalate is listed at 6.7 mg/L, or $6.7 \cdot {10}^{- 3} \text{g/L}$, far less than the $\text{1 g/L}$ threshold used to distinguish between soluble and insoluble compounds.