Wanting, to make up completeness; wanting, as regards a requirement; not sufficient; inadequate; defective; imperfect; incomplete; lacking; as, deficient parts; deficient estate; deficient strength; deficient in judgment.
When an introvert is quiet, don't assume he is depressed, snobbish or socially deficient. Laurie Helgoe
You should carefully study the Art of Reasoning, as it is what most people are very deficient in, and I know few things more disagreeable than to argue, or even converse with a man who has no idea of inductive and deductive philosophy. William John Wills
Being-alone is a deficient mode of being-with; its possibility is a proof for the latter. Martin Heidegger
After all, it is the divinity within that makes the divinity without; and I have been more fascinated by a woman of talent and intelligence, though deficient in personal charms, than I have been by the most regular beauty. Washington Irving