To render obscure; to darken; to make dim; to keep in the dark; to hide; to make less visible, intelligible, legible, glorious, beautiful, or illustrious.
obsequious
obedient or attentive to an excessive or servile degree.
obsolete
no longer produced or used; out of date.
obstinate
stubbornly refusing to change one's opinion or chosen course of action, despite attempts to persuade one to do so.
obstreperous
noisy and difficult to control.
obtuse
blunt/stupid
obviate
To anticipate and prevent or bypass (something which would otherwise have been necessary or required).