What does it mean to accept a job offer
There are many different takes. “Accepting” a job offer is pretty much that: if you tell the person who offered you (your HR contact, the hiring committee, any person of authority in the hiring process) that you accept their offer, that you take the job.

Does it mean there's not turning back? Of course not! The question then becomes: how binding is that agreement? And again, there are answers on many different levels: legal, moral, diplomatic…


Legal: as always, better ask a lawyer, union representative or knowledgeable and trusted friend. Everything depends on the local law, the type of offer made, what you said and/or wrote, etc. It may sound logical that nothing's set in stone until you have signed a contract, but that may not always be the case. Some institutions might, for example, require you to write and sign a binding letter of engagement before the contract is drafted (which, as you said, can take time). In some jurisdiction, the simple fact of showing up for work on the first day of the contract is a binding, implicit contract following the terms of your offer. (Though I would say it should be obvious to all that actually coming to work is pretty binding.)
Moral: that's the most variable of all. Turning down an offer you had accepted orally, because you now have a better offer from some other place, is not wrong in itself. The important thing is: being of good faith, and being diligent to inform them that you have changed your mind. If it turns out that you have accepted the offer, knowing all the while you would end up turning it down, that would be unexcusable.
Diplomatic: people understand the position you're in, as they have most probably been through it themselves some year back. So, they will be sympathetic, as long as they feel you are of good faith, diligent and show acceptable contrition (not sure that's the right term for what I'm trying to describe… let's say you look/sound apologetic enough). Otherwise, well, you risk make enemies and that may not be the best thing to do early in your career.


The fact is: the game is played by both sides. Hiring committees don't dismiss all other candidates immediately when they offer you a position, and they know that Stuff Happens. In a competitive environment such as academia, they surely have a plan B (and probably C and D).

Finally: if that's a tenured or tenure-track position, you'll probably stay very long (life?) there. It's an important choice, and thus you shouldn't find yourself bound by promises made too fast, or you may come to regret it.