Question

What does it mean if something is hyposmotic to another thing?

Answer 1

Osmolarity is basically a measure of fluid concentration relative to solute concentration inside a compartment (compartment almost always means a cell or a membrane bound organelle like a lysosome within a cell).

When something is hyposmotic to another comparment - for example, when a cell is hyposmotic to the environment in which it lives - it means that it has lower osmolarity than the external environment.