How do we define "density" for a solid?

$\text{Density,}$ $\rho$ $=$ $\text{Mass"/"Volume}$
So, the measurement is typically $\text{mass per unit volume}$, and for chemists, we thus get units of $g \cdot m {L}^{-} 1$ or $g \cdot c {m}^{-} 3$.