What does it mean if

It means if you think you are attracted to him, stay away from him.

So they don’t bother him and leave him alone. Ive done it also to kinda keep people away with that shit

He's ashamed of being single and lying. I once had a coworker who would sometimes speak of his "girlfriend" but would have nothing to say when asked for more info. He claimed to another coworker that he had 3 girlfriends. This coming from a guy that looks like a crossbreed of bozo the clown and super mario........

He is either very insecure or a chancer and wants to impress others for reasons unknown. I would avoid him.

quick way to diffuse workplace relationships. maybe bad experience in the past. who knows...

Probably wants to stay single and doesn't want to deal with questions or suggestions.

He’s gay

Maybe someone is chasing him so he lies hoping it will get to the other person and he won’t have to reject them.

Smart way to avoid. Lol

How do you know they are single?

He likes her but she dont wanns have a thing to do with him or shes married