Synset

dignified and somber in manner or character and committed to keeping promises
<adj.all>   freq. cnt.: 11 freq. cnt.: 5 freq. cnt.: 4 freq. cnt.: 2

grave

sedate

sober

solemn

sample sentences

"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"