sedate

(verb) cause to be calm or quiet as by administering a sedative to. Synonyms: calm, tranquilize, tranquillize, tranquillise. Examples: "The patient must be sedated before the operation."

(adj) characterized by dignity and propriety. Synonyms: staid.

(adj) dignified and somber in manner or character and committed to keeping promises. Synonyms: grave, sober, solemn. Examples: "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."