Though it may be impossible to "define" what "hard to manage" means, it seems that we all have a common understanding of what this term is getting at, and I am interested in getting down to just what this common sense term really means, and how we can take positive action based on its use.
While definitions will vary between managers as one guy's hard to manage can be another guy's star performer, the key is "hard to manage" people cause more work for the manager.
So what causes more work depends in part on manager personality and organizational culture.
But, in general, managers look for people who like to work in similar ways to how they want them to work. A micromanager is going to find a person who hates process hard to manage. A laizzez-faire manager is going to find someone who is pedantic and must have every i dotted and t crossed to be hard to manage.
Most managers find people hard to manage who can't live within the company policies, whatever they are. So if you have to do a timesheet daily and the manager has to hound you every day to do it, you are hard to manage. Most managers would classify employees who can't get along with others whether they like them or not as hard to manage. Most managers would have a problem with a person who is perceived as unreliable.
As someone who is applying for jobs, I don't need to worry about being classified by a particular hiring official as potentially hard to manage as it means that it is a place where I am unlikely to be happy anyway.
As a hiring official, it is indeed something to look for, but how you judge it would vary from person to person and organization to organization.
Hard to Manage:
May know field well but does not have common sense. Without having common sense a manager feels this employee could literally do anything at any time.
Person is sociably challenged.
Person is too needy.
Very close cousin to point #3 is the person talks/gossips too much. Throw in the type that debate every small task and need to know the "big picture" on a 10 minute to-do.
Person needs to be told everything. While needy may mean they come over for help on everything, someone who has no motivation beyond being told what to do sits there unproductively unless given tasks. Usually very specific tasks.
The manager simply finds you annoying or doesn't like your personality.
Someone who will disrupt other employees. Whether this is pissing them off, the way they look, cause fights, whatever.
You don't have the skill set. Instead of debating that with you they just tell you whatever.
If someone told me I seemed "Hard to Manage" after an interview I would have to think about what happened at the interview:
did I display some annoying trait, not seem attentive, talk too much, or come off as arrogant.
was the company and the manager a good fit for me. For instance I have grilled some "tech" managers when I have interviewed because I realized they weren't technical and do not wish to work for someone that has no idea or conception of the staff jobs. That is my choice. I made it known in that interview that I would not be a good fit and "hard to manage".
on the same point a lot of hiring managers may label good candidates like that and it comes across at my company. This is because they are fearful that candidate is more talented than them and they are looking out for themselves.
If you are just looking to get A job, ANY job than this is very negative. You need to work on your interview skills if people are telling you this and I would get a friend(s) involved. Most people I interview that I also believe have the skillset I would never label as hard to manage. So something is going on during the interviews. Now if you want a perfect environment/boss and you are interviewing them, you could be seen as hard to manage to a lot of interviewers.
From a Managers perspective there is one major reason you would call someone hard to manage. It means, they have personal issues or quirks which require your attention.
The could be social awkwardness, abrasive personality, insubordination or even unavoidable things like frequently sick.
The key is how much time must be spent on them. An easy to manage employee is one who you spend little to no time managing, they sort themselves out.