What is it called when you trim a royal palm tree?

In 99% of cases you cannot trim the height of a palm tree without killing it. Palms are moncotyledonous, this means they have one growth point or apical bud; this is located in the centre of the fronds and produces the new fronds. If this is damaged the plant cannot grow any more and will eventually die.

You do however also get "clump-forming" plams, in this case the taller plants can be removed and the smaller ones left to grow up and replace the ones removed