Sentence:  Soul of mine Drink in their matchless aspect as they lift Their circling range, obscured by <WSD>overdrift</WSD> Of cloud, or stand out sharply, line on line Of august shapes, upon whose foreheads shine The dawn's bright earnest and the late last Gift Of day, the brief empurpled gleams that shift Through netted vapors at the sun's decline. 
Meaning of the word marked with <WSD> tags:  Material that has drifted over something.