In a manner that involves boasting; while bragging or speaking with excessive pride.
Boasting (present participle of boast) + -ly. An alternative adverbial form emphasizing the action of boasting itself rather than the quality of being boastful.
English loves giving us multiple ways to express the same idea—'boastfully,' 'boastingly,' and 'in a boastful manner' all work, letting writers pick the version that sounds best in their sentence!
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