What does the term mean 'JAVA is not scalable' when it comes to web applications?

Not a term I'm familiar with. I was under the impression that java can be highly scalable under many circumstances; it just depends on the programmers and the builds design to really plan for scalability among other things.

@dalastTomCruise it's a accusation I've heard from a MEAN developer

(useless advice..) Means java doesn't like its weight being taken...

Much as I dislike Java, it is entirely scalable. Whoever said it isn't doesn't know what they're talking about.

It means the person saying that is trying to be fancy pants

It is wrong. Java is highly scalable.
If you write it properly, then you can scale it well.
Not only java, other languages too.