A waxy substance found in the head of a sperm whale, used to make candles and ointments.
Spermaceti is a special thing that comes from a big sea animal. People used to use it to make light and medicine.
Examples:
Spermaceti was used to make candles long ago.
The sailors found a lot of spermaceti in the whale's head.
The spermaceti made the candles burn very bright.
I heard that spermaceti was also used to make ointments.
The spermaceti from the whale was very valuable.
The spermaceti made the room very bright and smelled nice.