Corpse, Remains
noun
You leave behind your body to join the spirit realm. This body remainder is your corpse or remains.
いたい
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
どうして犯人が遺体の唇を舐めたのかは不明です。
We have no idea why the murderer licked the corpse’s lips.