怖い (kowai) means “scary” | MotiTan Japanese Dictionary

More examples

夜に一人で歩くのは怖いです。yoru ni hito ri de aru ku no wa kowa i de su

Walking alone at night is scary.

Covers both the fear felt by someone and the person, thing, or situation that causes it.

恐ろしいosoroshii: Causes a great deal of fear or seems very threatening.
おっかないokkanai: Causes fear and has a strongly casual tone.

恐れや不安を感じるさま。また、そうした気持ちを起こさせるさま。oso re ya fu an o kan ji ru sa ma ma ta sō shi ta ki mo chi o o ko sa se ru sa ma

The native Japanese adjective 怖い (kowai) comes from the older form こはし (kowashi), meaning "frightening" or "severe," through こわし (kowashi).

In casual speech, 怖い (kowai) can be repeated as 怖い怖い (kowai kowai) to show an immediate, strong reaction.