Euler force ($-m\dot{\mathbf{\Omega }}\times \mathbf{r}$)

A mass $m$ in a rotating reference frame with varying angular velocity experiences this apparent force. Dividing it by $m$ gives the Euler acceleration.

When a reference frame has time-dependent angular velocity $\mathbf{\Omega }(t)$, a particle at position $\mathbf{r}$ has apparent Euler acceleration $-\dot{\mathbf{\Omega }}\times \mathbf{r}$.