Depending on your views and which side takes your fancy most observers will tend to believe that an accepted definition of terrorism can't be agreed upon. The saying one man's terrorist is another man's freedom fighter comes up regularly in these debates. Obviously, there is a red line in my opinion for those to be definitely called terrorists who deliberately attack civilians.
Anyway, the founding fathers of Israel resorted to terrorism. The Zionist organisation Irgun was described as a terrorist organisation by the United Nations, British, and United States governments. The bombing by the Zionist terrorist group of British headquarters at the King David Hotel killed 91 people was one of the most lethal terrorist attacks of the 20th century and was one of the factors the British left. Terrorism in parts helped form Israel.
Over the last few decades, Mandela was called a terrorist, Modi was barred from entering the UK, EU and USA whilst presiding in Gujarat during the massacre of over 1000 Muslims and is now the Prime Minister of India.