When a solution is not completely saturated with a substance, it is in a state of subsaturation.
Subsaturation means there is room for more of the substance to dissolve.
Examples:
The water is in a state of subsaturation because more sugar can still dissolve in it.
The subsaturation of the air means it can hold more moisture.
Subsaturation is when there is still space for more stuff to mix in.
The subsaturation of the soil means we can add more fertilizer.
The subsaturation of the market means there is still room for more products.
The subsaturation of the sponge means it can soak up more water.