"A second colleague at a different institution held me against a wall against my objections and struggles and hit me with objects for his own amusement."

Now this sounds rather as an assault, a sick power play, but I would accept it called rape when it involved was sexual amusement but probably sexual assault would be a better term as it would not dilute the meanings confusingly.

Nonetheless this kind of behaviour is sickening and not acceptable by any means but it would explain why it was possible to tolerate it multiple times and how hard it was to do anything to prove that it happened.

Edit:

I think that it would be much easier to fight with such behaviour by calling it by actual names.

For example "Stop sexual assaults at work" would be in my opinion much more convincing and believable slogan than the exaggerated wording.

This would make the fight with the problem easier as it would not create that much confusion and opposition from it.

Using strong words creates opposition as people would find it by their own experience rather not believable but perhaps they have seen, heard something that would fit sexual assault definition or sexual harassment definition.

I believe that it would be much easier to define and establish the definition of sexual assault in peoples minds and educate them to see it than trying to redefine the established definition of rape in the society.

For clarification, I consider here acts that are described by

"A second colleague at a different institution held me against a wall against my objections and struggles and hit me with objects for his own amusement."

Now again, we should not tolerate this kind of behaviour and we should fight against it but I think it would be easier when we do not call it by too strong names as it would be then easier to establish this as wrongful and not acceptable behaviour in peoples minds.

I think that it is easier to fight with concrete problems individually rather than stretching the definitions.