hebetudinous

heb•e•tud•in•ous (heb-i-tood-n-uhs) / he-bə-ˌtüd-ə-nəs/   adj

Definition 
1. dull or lethargic, especially relating to the mind

hebetude noun

Related
Synonyms: lethargic, languorous, listless, debilitated, dilatory, dull, enervated, laggard, languid, languorous
Related Words: hebetate (to dull)

Examples
•“But somehow trouble always finds you,” Miss Devlin retorted, angry, but not sure why. “I've always suspected men like you wear guns in a futile effort to disguise your hebetudinous natures. The word "hebetudinous" rolled off Miss Devlin's tongue with the all the ostentation of the wise preaching to the foolish. It wouldn't be the first time she called a man stupid to his face with a word he couldn't understand. 
• The audience waits in a kind of hebetudinous fixation, perhaps astonished at the perfectly sustained level of mediocrity.
• Some of their proposals are sufficiently platitudinous — and hebetudinous — to convey antidote with their bane. Others, however, cannot thus be dismissed.

The Storyline
Just as suddenly as the hullabaloo arose, a now decidedly hebetudinous Kurt began mumbling Anna's name through the door.

Origin
1620s, from L. hebetudo, noun of quality from hebes “blunt, dull.”

Sources: Wordsmith, Online Etymology

Why This Word:
Hebetudinous isn't so rare that you can be certain that you'll never stumble upon it. And when you do, you wouldn't want to seem... hebetudinous. As one of the quotes aver, hebetudinous has a pretentious quality about it in use, which frankly is part of its appeal. But getting past that, it lies in the space mapped out by the intersection of dullness and lethargy and that starts to paint the picture. Who among has not encountered a hebetudinous youth whose mental dullness seems to stem more from a lack of motivation than ability? And now you can point that out to them without fear of them being able to take offense.

Word-E: A Word-A-Day