Hmm. I've never heard the word "conjecture" to be honest. 

Its definitely a more beneficial term.

The scientific process works like this: First, I propose a hypothesis or conjecture - this is something I want to check about the world to see whether it is true or false. An example of a hypothesis or conjecture is "the Earth is flat." Typically, you'll have some evidence supporting the conjecture.

The next step, where the flat-earth community has gotten it horribly wrong, is that you must attempt to *disprove* the initial conjecture. This attempt must be rigorous. Your methods must leave no doubt that you were genuinely trying to disprove it. The conjecture cannot progress to the level of "theory" until you have convinced the scientific community that it cannot be disproved.

That's what separates "theory" from "a collection of conjectures." In my understanding, a set of ideas can't reasonably be called "theory" until it has survived the scientific process for a long time. This definition doesn't work perfectly, because you still have various things out there called Theory that contradict each other - you actually see this quite a lot in theoretical physics.