  We study weakly invertible cells in weak $\omega$-categories in the sense of
Batanin-Leinster, adopting the coinductive definition of weak invertibility. We
show that weakly invertible cells in a weak $\omega$-category are closed under
globular pasting. Using this, we generalise elementary properties of weakly
invertible cells known to hold in strict $\omega$-categories to weak
$\omega$-categories, and show that every weak $\omega$-category has a largest
weak $\omega$-subgroupoid.
