Fascinated
Enthralled definition: captivate
The closest word to captivate is fascinated.
Hope this helps :))
Explanation:
Whitman compares Lincoln's tragic death to a captain lying dead on the deck of his ship. ... He reminds the living of the sacrifices that the dead made for them.
This means that he feels very drugged as if he had just taken an opioid or something. He hears a nightingale singing saying that the bird is spreading its happiness too much. He is also saying that he too is happy because he can hear the nightingale sing somewhere amidst the forest.
