In a Facebook discussion, one friend described macroevolution as such.
Macroevolution is microevolution given enough time.
In response from a creationist friend (yes, I maintain them), he got this.
Here is a fuller explanation of the terms from yours truly. Enjoy.
[That person's] explanation is apt. First, it addresses the terms to the extent that they probably deserve. No scientist uses them in any meaningful way, except when addressing the invalid issues of creationists. And that’s the truth: the terms are largely of creationist origin. They arose as a means to appear more reasonable to the public. Similarly, there is a strategy going around creationist organizations known as “strengths and weaknesses”. It seeks to make creationists seem more reasonable. In truth, we’re just seeing an extension of normal creationist coyness from the organized among the crowd (i.e., the Discovery Institute & friends).
But insofar as the terms mean anything, one is just a description of the other on another scale. Here’s why.
Evolution is a continuous process. At no single point in history can anyone point and say, yes, here is where species X began. Natural selection works gradually and cumulatively. It is simply a matter of convenience that we can separate species. All their ancestors are gone to say otherwise. In other words, a mother dinosaur only gives birth to daughter dinosaurs. But gradually, those dinosaurs change into something slightly different. Over wide expanses of time, those slight changes add up to big changes. This should be a hugely simple concept. Feathers, webbed feet, webbed arms, lighter frames. This all eventually add up to the evolution of birds. (Some scientists consider birds modern day dinosaurs, a somewhat trivial issue.) But at no point did a dinosaur lay an egg which hatched into an eagle. It took a huge number of small changes to lead that bird. That is what microevolution does over thousands and millions of years to produce macroevolutionary changes which can only be identified in hindsight, eons later.