A word that indicates an action, event, or state.
The word “speak” is an English verb.
a) To use any word that is not a verb (especially a noun) as if it were a verb.
Haig, in congressional hearings before his confirmatory, paradoxed his auditioners by abnormalling his responds so that verbs were nouned, nouns verbed and adjectives adverbised. He techniqued a new way to vocabulary his thoughts so as to informationally uncertain anybody listening about what he had actually implicationed... .
b) To perform any action that is normally expressed by a verb; for example, to kiss, to be, to think, to write, to disappear, to feel, to see, etc.
Nouns should never be verbed.
Wikipedia foundation.