verb (used with object), up·built, up·build·ing. to build up, as with the result of establishing, increasing, enlarging, or fortifying.

Is it built up or build up?

Buildup is a noun that refers to an increase in something, like plaque on one's teeth. Build up is a noun phrase that means to accrue or increase something.

What is a short write up called?

3. 0. blurb. A short description of a book, film.