A Zionist is a follower of Zionism, a movement that created and supports Israel as the official state for Jewish people in Palestine. The term can be a neutral, positive, or offensive term for a Jewish Israeli nationalist.
Its basic definition is flawed to begin with by defining the area that Jews have wanted to live for millennia by the name it was given by the Romans to erase Jewish history there: "Palestine."
The second sentence of the definition is also simply wrong: many Zionists are not Jews.
A dictionary should note that the word is used as an epithet by some. But Dictionary.com goes way beyond that, using only negative examples of the word, and misrepresenting them as well.
Its "related words" box has absolutely nothing to do with Zionism, and except for the Ten Commandments, they are all offensive.
Things get much worse.
Every example of its use comes from rabid haters of Israel.
The first comes from some random tweeter who refers to the "zionist apartheid regime" - who on Earth would choose that as a representative example?
The second is worse, as it pretends to be quoting Jewish Telegraphic Agency but in fact it is quoting Jeremy Corbyn.
The third is a photo of a tiny Jewish anti-Zionist sect.
And it doesn't end there. The illustration of "Zionism" used in its discussion of the origin of the word is the notorious Map That Lies, credited to anti-Zionist site Mondoweiss:
WTF?? The lying map has zero to do with Zionism and everything to do with anti-Zionist and antisemitic propaganda.
And even this section is inaccurate:
Zionist activism continued into the 20th century. The word Zionist became so closely associated with Jewish politics that antisemites weaponized up the term. The 1903 Protocols of the Elders of Zion, for instance, notoriously fear-mongered a Jewish state in Palestine as just the first step toward their masterplan of world domination.The Protocols forgery had nothing to do with Zionism. It was pure antisemitism.
It then goes on to say that many people use Zionist pejoratively, and gives even more examples!
Not once does it mention that anti-Zionism is often a cover for antisemitism, which is in fact how it is used most of the time nowadays.
There is not a single example of using the word Zionist in a positive way. Not one. The people who coined the term don't get to define it.
This is a reference site on the Internet, and Google uses it as an authoritative source. If this is how it defines Zionism, then if Dictionary.com has any integrity at all, people should be fired for politicizing a dictionary entry to incite hate.
(h/t Mitchell Bard)
UPDATE: Dictionary.com got rid of the offensive examples and changed the definition. The entry isn't perfect but it is much better.