Στυγνάζω means to have a gloomy, dark, or lowering look—used of both facial expressions and threatening weather. In Mark 10:22, the rich young ruler becomes gloomy (literally 'having become dark in countenance') when Jesus tells him to sell all and follow. His face falls because the cost is too great. In Matthew 16:3, Jesus refers to a threatening, overcast sky that signals coming storms, using weather-reading as a metaphor for discerning spiritual signs. The verb captures the visible darkness that appears on face or sky when trouble approaches.