A posteriori is something "relating to or denoting reasoning or knowledge that proceeds from observations or experiences to the deduction of probable causes."
It constrasts with a priori that is, instead, something "relating to or denoting reasoning or knowledge that proceeds from theoretical deduction rather than from observation or experience."
The first expressions that you asked for, then, is used when you assert or state something after having observed the subject of the matter. You can read more about these two terms in their wikipedia page.
Posterior means the back part of a body, or something coming after.
Note: The emphasized parts are taken from the NOAD.
You defame by publishing information hurting good reputation - possibly embarrassing, claiming incompetence or negligence.
You vilify if you defame by presenting the person's actions to be evil. Posting photos of someone sleeping under a tree, drunk may be defaming. Photo of that person raising a hand on a child is vilifying. Also, presenting normally mostly benign actions, making them to appear as evil is called vilifying (e.g. claim a woman who wears a red dress is "dressing like a whore")
Slander is a defamation that is false. (note for a long time in England one could win a lawsuit for defamation even if the defaming claim was proven true. Slander is always a defamation which is a lie)
I'm sorry but I won't give you any details on calumniate, I can only guess that's not a very frequently used synonym for slander. I think it implies verbal (or textual) form of slander, which on itself may take other forms (performing, parodying) but don't quote me on that.
You should also note libel (per StoneyB's comment) which is the same a slander except committed in a fixed/permanent form - slander is always in a volatile form (speech, gestures), while libel is fixed - in writing, as a picture, video, voice recording etc.
Best Answer
A venue is a special kind of place:
Thus all venues are places, but not all places are venues. Your house, for example, is a place. The stadium in your city is a venue. Your house could be a venue, however, if you were to host some kind of gathering there.