莽 rarely stands alone in modern Chinese — it lives mostly in compounds: 莽原 (wild grassland), 草莽 (the wilds; lawless lands), 鲁莽 (lǔmǎng, reckless), 莽汉 (a brutish guy), 莽撞 (rash). On its own it has a literary feel.
memory
The 艹 (grass) radical on top hints at the original meaning: thick, untamed grass. From there it stretched metaphorically to "wild and lawless" → "a reckless person." Same logic as English "rough" going from terrain to behavior.
