숙연해요 · 숙연했어요 · 숙연한 (+noun)
solemn, hushed, grave (mood)
Example
묵념이 시작되자 분위기가 숙연해졌어요.
When the moment of silence began, the mood became solemn.
Word parts
숙 solemn+연 -like
Literally 'in a solemn manner'.
Good to know
Usually describes a mood or people becoming solemn: 숙연해지다.