Learn Danish: Støjen fra naboen er ikke til at holde ud. - The noise from the neighbor is unbearable.

It literally translates to "not to endure" or "not to hold out". The grammatical structure er til at followed by an infinitive is a common way to express that something is possible to do. Adding ikke makes it impossible, meaning the noise here is impossible to endure.

What does the phrasal verb "holde ud" mean on its own?

At holde ud means "to endure", "to bear", or "to stand" something. It is made up of holde (to hold) and ud (out). You can easily remember it by thinking of the English phrase "to hold out" in a difficult situation.

Why is the word for noise written as "støjen" instead of just "støj"?

Støjen is the definite form, meaning "the noise". Just like in English, because you are talking about a specific noise (the one coming from the neighbor) rather than noise in general, you must attach the definite suffix -en to the noun støj.

Could I use a single adjective like "ubærlig" (unbearable) instead of this long phrase?

Yes, you could say støjen er ubærlig. Both are grammatically correct, but the phrase ikke til at holde ud is much more common and natural in everyday spoken Danish when complaining about things like noise, bad weather, or minor pain.