1) Common way to swear 2) Gravely 3) Gravely and sedately 4) How to behave in church 5) How to swear 6) In a grave and sedate manner 7) Sadly 8) Seriously 9) Soberly 10) With seriousness 11) Without cracking a smile 1) Gravely 2) Grimly 3) Miserably 4) Sincerely 
• (adv.) In a solemn manner; with gravity; seriously; formally.
Sol'emn·ly adverb In a solemn manner; with gravity; seriously; formally. « There in deaf murmurs solemnly are wise.» Dryden. « I do solemnly assure the reader.» Swift. 
[adv] - in a grave and sedate manner
adverb in a grave and sedate manner; `the judge sat there solemnly`