what are words with the prefix ob?
['obstacle: that which stands “against”', 'obligation: that which ties “towards” you.', 'obtain: “thoroughly” hold onto.', 'obfuscate: “thoroughly” darken.', 'obtuse: of being “thoroughly” mentally dull.', 'obdurate: “thoroughly” hard, and so stubborn.', 'obstreperous: “thoroughly” make noise.', 'occupy: “thoroughly” take.']