Ghost
Specter, Spectre, Phantom
noun
A secluded ghost is someone who's secluded and a ghost, because everyone's forgotten about him (thus the "ghostness" of him). This thing is a ghost or specter.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
「今日、学校サボってゲーセン行こうぜ。人生は一度っきりだしな！」「そうかな。僕はよく幽霊を見るから、死後の世界を信じてるんだけど。」
"Let’s skip school and go to the arcade today. YOLO!" "I don’t think so. I see ghosts all the time, so I believe in a world after death."