to climb to the top of something that is high and difficult to climb:
Rescuers had to scale a 300m cliff to reach the injured climber.
to make writing or a picture the right size for a particular purpose
scale something to something
The writing can be scaled to any size, depending on the paper.
to be extremely successful:
By the age of 21 he had already scaled the heights in the academic world.
scale something ↔ down/backphrasal verb
The emergency aid programme has now been scaled down.
scale something ↔ upphrasal verb
Production at the factory is being scaled up.