惶 is a bound form (b.f.) — it never stands alone as a word. You will encounter it as the first or second element in literary/formal two-character compounds such as 惶恐 (huángkǒng, 'terrified'), 惶惶 (huánghuáng, 'anxious/panicky', as in 人心惶惶), and 惊惶 (jīnghuáng, 'alarmed'). All of these carry a strong sense of fear, anxiety, or panicked fluster. Use it only within these set expressions.