Wiktionary
submoronic
a. Having, or suited to, an intellect below that of a moron.
Usage examples of "submoronic".
During these periods when he couldn't spare time for himself, the garden was cared for by an elderly Sicilian deaf-mute of submoronic intelligence but absolute trustworthiness with growing things—his ancestors had trained vines and coaxed hedges for the ancient Romans.
It was Anselmo, he could tell from the corner of his eye—no mistaking that hand like a bleached ham, that face big as that of a white horse, for in addition to being a submoronic deaf-mute, the ancient Sicilian had acromegaly.
They're thrown back to a submoronic level—a lot of them must simply die out, unable to survive without minds.