  The antineutrino scattering channel $\bar{\nu}_{\mu} \,\text{CH} \rightarrow
\mu^{+} \,\pi^{-} \,X$(nucleon(s)) is analyzed in the incident energy range 1.5
to 10 GeV using the MINERvA detector at Fermilab. Differential cross sections
are reported as functions of $\mu^{+}$ momentum and production angle, $\pi^{-}$
kinetic energy and production angle, and antineutrino energy and squared
four-momentum transfer. Distribution shapes are generally reproduced by
simulations based on the GENIE, NuWro, and GiBUU event generators, however
GENIE (GiBUU) overestimates (underestimates) the cross-section normalizations
by 8% (10%). Comparisons of data with the GENIE-based reference simulation
probe conventional treatments of cross sections and pion intranuclear
rescattering. The distribution of non-track vertex energy is used to decompose
the signal sample into reaction categories, and cross sections are determined
for the exclusive reactions $\mu^{+} \pi^{-} n$ and $ \mu^+ \pi^{-} p$. A
similar treatment applied to the published MINERvA sample $\bar{\nu}_{\mu}
\,\text{CH} \rightarrow \mu^{+} \,\pi^{0} \,X$(nucleon(s)) has determined the
$\mu^{+} \pi^{0} n$ cross section, and the latter is used with $\sigma(\pi^{-}
n)$ and $\sigma(\pi^{-} p)$ to carry out an isospin decomposition of
$\bar{\nu}_{\mu}$-induced CC($\pi$). The ratio of magnitudes and relative phase
for isospin amplitudes $A_{3}$ and $A_{1}$ thereby obtained are: $R^{\bar{\nu}}
= 0.99 \pm 0.19$ and $\phi^{\bar{\nu}} = 93^{\circ} \pm 7^{\circ}$. Our results
are in agreement with bubble chamber measurements made four decades ago.
