Life is a Verb.
Although life can also be an adjective as an adjective is related to a noun because an adjective is a word or phrase naming an attribute, added to or grammatically related to a noun to modify or describe it.
Life is a verb and not a noun.
A verb is a word that in syntax conveys an action, an occurrence, or a state of being.
In the usual description of English, the basic form, with or without the particle to, is the infinitive. In many languages, verbs are inflected to encode tense, aspect, mood, and voice.
A noun is a word that is used to describe an action, state, or occurrence, and forming the main part of the predicate of a sentence, such as hear, become, happen.
Since life is a state of being or a life is occurring then that makes the word life a verb instead of a noun.
In life you're living which is a state of being so it's always a verb and not a noun.