In a way that is related to a noun or acts like a noun.
This word is used in grammar and is not very common in everyday talk.
Examples:
He used the word substantivally in his sentence.
She spoke substantivally about the importance of nouns.
Substantivally, the word 'happy' can be used as a noun.
I think she talks substantivally too much!
He knows substantivally everything about nouns.
She thinks substantivally is a funny word to say.