怖 is a bound morpheme (b.f.) meaning 'fear' or 'terror'. It cannot stand alone as a word; you will only encounter it as part of compounds such as 恐怖 (terrifying), 可怖 (horrible), and 白色恐怖 (white terror). When you see 怖 in a word, it contributes the sense of fear, dread, or fright.