What does short to ground mean? How to do that?
Short is an English word and is used almost in a slang/jargon type of way in Electrical Engineering. Short in English means that the length or distance of something is close by, or   it is over a relatively small distance.

The use of the word "short" in "short to ground" is actually short (lol!) for the full term "short circuit". To create a short circuit in Electronics, you basically remove everything in the way between one node and another, and directly connect them. Can be done numerous ways, but the simplest is of course a [short!] wire or PCB trace. 

The use of language in Electrical Engineering must make it very hard for non-english speakers to understand the strange things we say, and it can be quite a problem with international design/product collaboration. Even a problem for simple tutorials or online 'instructables'[not a real word by the way!] and causes grief all the time i'm sure of it!