Grinningly is an adverb that describes a person doing something with a wide smile. Other synonyms that could be used instead of grinningly include gleefully, smugly, joyfully, triumphantly, confidently, amusedly, elatedly, excitedly, smirkingly, and cheerfully. Each of these words conveys a slightly different emotion, but all suggest a sense of happiness or satisfaction. For example, one could say "James smirked gleefully" or "Susan smiled excitedly" instead of saying "James did it grinningly." Choosing the right synonym to convey the intended emotion or tone can add depth and variety to one's writing.