炽 is a bound form (b.f.) — it cannot stand alone as a word. In formal or literary Chinese it means 'blazing, fiercely hot' and appears as the first element in compounds like 炽热 (chìrè, extremely hot), 炽烈 (chìliè, burning fiercely), and 炽盛 (chìshèng, blazing with intensity). You will encounter it in weather descriptions, emotions (passion), and historical warfare contexts.