Debar, v. t. [imp. & p. p. Debarred; p. pr. & vb. n. Debarring.]
Etymology: [Pref. de- + bar.]
To cut off from entrance, as if by a bar or barrier; to preclude; to hinder from approach, entry, or enjoyment; to shut out or exclude; to deny or refuse; -- with from, and sometimes with of. Yet not so strictly hath our Lord imposed Labor, as to debar us when we need Refreshment. Milton. Their wages were so low as to debar them, not only from the comforts but from the common decencies of civilized life. Buckle.
Shades of meaning
Fernald has no entry of its own for debar; he lists it under prohibit.
Where he writes about it:
Debar is said of persons, disallow of acts; one is debarred from anything when shut off, as by some irresistible authority or necessity; one is prohibited from an act in express terms; he may be debarred by silent necessity. — from prohibit