What is the name given to a word instead of noun?

There isn't a single specific name for a word used instead of a noun. It depends on what kind of word is being used:

* Pronoun: This is the most common substitute for a noun. Examples include "he," "she," "it," "they," "we," "you," and "I."

* Noun phrase: This is a group of words that acts as a noun. Examples include "the big red ball" or "the woman in the red dress."

* Gerund: This is a verb ending in "-ing" that acts as a noun. Examples include "swimming" or "running."

* Infinitive: This is the base form of a verb, often preceded by "to." It can act as a noun. Examples include "to sing" or "to dance."

So, it really depends on the specific word being used and its grammatical function within the sentence.