惨淡 is a literary adjective with two distinct senses. The first describes a scene or atmosphere that is gloomy, bleak, or dismal — often used for weather, business conditions, or prospects. The second sense appears in the fixed expression 惨淡经营 (cǎn dàn jīng yíng), meaning 'to manage or operate with painstaking effort under difficult circumstances'. The two senses are unrelated in English, so context is key.