The settlers would probably have to commit an act of terrorism - to kill people at random to create fear (i.e. terror) for a political goal - to be defined as terrorists. Only Baruch Goldstein fits that description and he's one person. I hope that answers your question.
Three minors arrested in Jaffa for throwing rocks at a bus; no injuries reported (Haaretz)
from the article: Ultra-Orthodox Jews deliver a population boom to the West Bank