The definition of 'terror' is extreme fear. 'ism' at the end of the word 'terror' is a suffix to indicate that 'terror' represents acts and activities related to causing extreme fear, while 'terrorizing' is the act with the aim to cause extreme fear.

The word 'terrorism' refers to methodologies on which the use of terror is based. Anyone who resort in acts and activities with the intention to cause extreme fear, that person is a terrorist. But, when two or more people form, or people join the forming of a group with the intention to cause extreme fear, they are members of a terror group, not a terrorist group as that is a undefined political pleonasm. Here is why:

The aforementioned does not explain what kind of terrorist they are. Because terror-ist, so someone who spreads extreme fear, may also refer to a tyrant, an dictator, an autocrat even the military that has taken over an civilian ruling like in Myanmar.

Again, "terrorists" is a popularized collective name that is even used on social media against anyone who post content that is pro-Palestinian. This kind of brandishing have been since the speech by US President George W. Bush from September 20, 2001 when he introduced 'war on terror'.

Canada, the European Union, Israelis, Japan and the United States have designated Hamas as a terrorist organization. Australia, New Zealand, Paraguay and the United Kingdom have designated only its military wing as a terrorist organization (as of 2021). It is not considered a terrorist organization by Brazil, China, Egypt, Iran, Norway, Qatar, Russia, Syria and Turkey.

In December 2018, the United Nations General Assembly rejected a U.S. resolution condemning Hamas as a terrorist organization.

The question rises when is it correct to label Hamas as an armed terror organization?

Hamas is not residing in the Israeli occupied territory, is that territory was never consecutive and historically Israeli.  The Israelis do not live in time of peace as they never have lifted the their self-declared stage of war since 1967. That is why the United Nations still considers the Israelis as war belligerent. 

So, labeling Hamas as a "terrorist organization" is purely based on Zionized politics, not with criteria as written above.

According to Law Of Belligerent Occupation, occupation means a situation when, in during an international armed conflict, a territory, or parts thereof, comes under the effective provisional control of a foreign power. The latter brings us to Article 51 in the UN Charter:

Gaza is not a country. It is part of the occupied State Of Palestine. We can at least say that the occupation of Gaza have never ended despite the withdrawal from Gaza in 2005. This brings us back to the Law Of Belligerent Occupation that provides occupied people the right to form armed groups to resist occupation. Hamas is in this regard an resistance group, not an "terrorist group." The adamant stubbornness the Israelis always have been showing, that Hamas is a "terrorist organization" is to protect a long lived desire that their ancestors, the European migrants, brought into British Mandatory Palestine but introduced in Basel, Switzerland in 1897: Zionism.

Protocol I of the Geneva Conventions stipulates the provision of the right of self-determination when people are under foreign and colonial rule. The Israelis are descendants of European Zionist migrants, and currently a people from around the world. They all are not autochthonous to the region thus frankly foreigners.

The foreigners in the West Bank, actually in the whole of the occupied State Of Palestine, are of the same definition as those from Britain, France and the Netherlands when they went to the American continent more than 400 years ago to take the land of the indigenous people. Lots of wars were waged to remove these people there where the Europeans wanted to settle. That's how the United States and Canada came to exist. It is also the way how European Zionist migrants created theirs.

Members of the Hamas have the full right to resist the Israeli occupation of Gaza and the annexation of the West Bank. If they take and use that right, they must distinguish themselves from the civilian population, or on the basis of articles 43 & 44 of the Additional Protocol I of the Geneva Conventions, at least carry their weapons openly during attacks and deployments.