It is an abbreviation of the French word "Sainte", meaning "saint" or "holy" in English.
Here are some examples:
* Ste-Catherine (Saint Catherine) is pronounced "sahn-ka-trēn"
* Ste-Sophie (Saint Sophie) is pronounced "sahn-so-fē"
* Ste-Anne (Saint Anne) is pronounced "sahn-an"
Remember, the "e" at the end of "Ste" is silent.