I would suggest “Touch and hold”. Many users tend not to understand 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.