unsaturated solution

https://doi.org/10.1351/goldbook.15369
Solution that has a lower proportion of a solute than one that is in equilibrium with undissolved solute at specified values of temperature and pressure.
Source:
PAC, 2008, 80, 233. (Glossary of terms related to solubility (IUPAC Recommendations 2008)) on page 270 [Terms] [Paper]