"Son coeur est un luth suspendu;/Sitot qu'on le touch il resonne"
French for "His heart is a hanging lute;/Whenever one touches it, it resounds."
"which in sooth tarried not for his full coming"
which in truth did not wait for him to arrive
collocation
arrangement or juxtaposition
doughty
brave
ennuye
French for bored or apathetic
Fuseli
Henry Fuseli (1741-1825) was a painter in the Romantic style. He thereby participated in much the same artistic tradition which originally inspired Edgar Allan Poe. Noted for their grandiose intensity and wild imagination, Fuseli's paintings are referred to in this story as "reveries," reflecting the even more dreamlike, less "concrete" works of Usher.
hold parley
discuss or converse; negotiate with an antagonist
pinion
wing
porphyrogene
royal--in "The Haunted Palace," the implication is that the inhabitants of the palace are of royal descent (note that the ruler is called a "monarch")
prolixity
long-windedness. Much as Poe was famous for ripping apart works of literature in his reviews, here the Narrator flatly denounces the silly "Mad Trist" he reads to Usher as a way of calming both of them down.
seraph
celestial winged being
tarn
mountain lake, river
