In a grim manner; seriously, sternly, or with a forbidding appearance or demeanor.
Grim + -ly (adverb suffix). Grim comes from Old Norse/Germanic roots meaning 'fierce' or 'fierce-looking.'
Grimly is one of those adverbs that writers love because it conveys attitude instantly—'he smiled grimly' tells you far more than 'he smiled seriously' ever could.
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