A verb is a °root that denotes an °action.
"Verb" is defined here in notional terms, following Haspelmath (2023) (see also this blogpost: https://dlc.hypotheses.org/3467). Many authors define "verb" also (or alternatively) in terms of coding strategies, but languages show substantial differences in this respect. Many definitions of "verb" have the downside that one does not know how salient the grammatical properties need to be in order to single out a grammatical class (and distinguish it, say, from a formally defined adjective class).
verb (CXN) = the head of a verbal clause – that is, a clause that denotes an action. Example: the word jumped in the clause She jumped, is a verb – it is an action word that is the head of the clause and is predicated of She. (Sections 2.2.3, 6.1.1)
"The class of verbs in any language is the grammatical category that includes lexemes which express the least time-stable concepts, e.g., events such as die, run, break, etc." (Payne 1997: 47)