Is the word were a noun?

No, "were" is not a noun. It is a verb, specifically the past tense plural form of the verb "to be".

Nouns are words that name people, places, things, or ideas. Verbs express actions or states of being.

Here's an example:

* Noun: The children were playing in the park. ("Children" names a group of people)

* Verb: The children were playing in the park. ("Were" expresses a state of being in the past)