How noteless men and
The poem repeats
The entire poem appears twice—verbatim repetition. Like a song's chorus, or like obsessive grief circling back to the same questions.
Pleiads = star cluster
The Pleiades, also called the Seven Sisters—a cluster of stars visible to the naked eye. Dickinson equates ordinary men with celestial bodies we barely notice.
wrapt = wrapped
Old spelling of 'wrapped'—meaning shrouded, hidden, taken away. Death makes someone disappear as suddenly as a star vanishing from view.
Dickinson's coinages
She invents 'leagueless' (unmeasurable) and 'O'er-take-less' (impossible to catch). The living exist in a state we can't measure or hold onto.
deign = condescend
To deign is to lower yourself to do something beneath you. The heavens won't even condescend to explain why people die.