Sentence:  Stellar <WSD>occultations</WSD> potentially provide the highest precision data for relating solar system ephemerides to the stellar reference frame. For example, <WSD>occultations</WSD> by the Uranian rings can define the position of the occulted star relative to the rings to better than 0.02 mas (equivalent to a few hundred meters at the distance of Uranus). <WSD>Occultations</WSD> by atmospheres can be less precise than <WSD>occultations</WSD> by symmerical solid bodies, like rings and large asteroids, with a precision on the order of 1.0 mas. 
Meaning of the word marked with <WSD> tags:  An astronomical event that occurs when one celestial object is hidden by another celestial object that passes between it and the observer when the nearer object appears larger and completely hides the more distant object.