QUIETLY SERIOUS' The term 'Quietly Serious' can be summed up as a combination of two words: SOLEMN and Quiet. SOLEMN is an adjective that means having or expressing a serious attitude or demeanor, often with a hint of sadness. Quiet is an adjective that means making little or no noise. Together, these two words describe someone who is serious and thoughtful, but not loud or boisterous. They are the type of person who prefers to observe and reflect rather than speak out.