Sentence:  By observing a <WSD>smirch</WSD>, LISA offers a unique opportunity to directly map the spacetime geometry around the central object and test whether or not this structure is in accordance with the expectations of general realtivity. 
Meaning of the word marked with <WSD> tags:  A chirp of radiation power from an astronomical body that has a smeared appearance on its plot in the time-frequency plane (usually associated with massive bodies orbiting supermassive black holes)