done, said, etc. in a serious and committed way
performed with religious or other ceremony; formal
"a grave God-fearing man"
"a quiet sedate nature"
"as sober as a judge"
"a solemn promise"
"the judge was solemn as he pronounced sentence"
"both sides were deeply in earnest, even passionate"
"an entirely sincere and cruel tyrant"
"a film with a solemn social message"
His holy Rites, and solemn Feasts profan'd.