I've seen both versions used in Android. What do you think is the best term to use? I've also heard people to use "Long click", "Long touch" & "Long tap" but I personally don't like any of those. It would be nice to finally get some standard for this terminology.
Well, if this is for Android, chances are you're using Material, and according to Material Design guidelines, the proper term is long press
I would suggest "Touch and hold". Many users tend not to understatement the term "long" in longpress. Therefore "Press and [then] hold" is a better description of the action.
OK, due to the comments below, here is a more descriptive answer :-)
"Longpress" means "press for a long time".The word "long" comes first but that is the second action the user has to commit. We also have to tell the user how much time (s)he shall spend during that "long" time.
The word "longpress" is not (yet) a term that common people understand.
So, every term beginning with the word "long..." aught to be avoided.
"Press and hold" on the other hand tells the user to 1: press on the item and then 2: keep on doing so until something else happens, something that will inform the user (s)he can release his/her finger from the device.
For my opinion "Touch & hold", because it explains user action in details.