The adjective gleeful and related noun glee are at the root of gleefully, all of them sharing the Latin root word gliu, "entertainment, mirth, jest, or play."

Is gleefully an adverb or adjective?

gleefully adverb - Definition, pictures, pronunciation and usage notes | Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com.

What is the definition for gleefully?

: full of glee : merry gleeful laughter.