It is a verb.
Running can be a verb (present participle) or a noun (gerund).
It would be a verb, just like "running" is a verb.Examples:He was running forward.He was lurching forward.
Your running list of new vocabulary words
Keeping is the present participle of the verb keep.
Word, Part of speech, and definition.
"Wildly" is an adverb . . . it modifies a verb (action word). "He was running around the yard wildly". 'Wildy' modifies the verb, 'running'.
A vocabulary list should always include the pronunciation, if unusual, the part of speech, and possibly a close synonym or related word.
part of speech
The part of speech for this particular word is a noun.
The part of speech for "answer" is a noun.
adverb
what part of speech is beneath