I think everyone agrees that a descendant is "One whose descent can be traced to a particular individual or group" (American Heritage Dictionary). That same dictionary defines an ancestor as "A person from whom one is descended, especially if more remote than a grandparent; a forebear."
Many genealogists, although agreeing on the definition of "descendant," have a wider definition of "ancestor" which includes aunts and uncles, perhaps even some older cousins. They use the term "direct ancestor" when they want to weed out the avunculars and their female equivalents.
But I have yet to see any reference to a MRCDA - Most Recent Common DIRECT Ancestor - that basic target of much of our research. Genealogists use MRCA to define how two people are related. As in "Mordecai Meir Kwoczka is your great-grandfather and my great-great-grandfather" - our Most Recent Common Ancestor.
So Linda's father and my father are brothers. Both are more recent than our grandparents, who would be the traditional bearers of the MRCA title. So would their sister, our aunt. Our parents and their siblings are by definition more recent than our grandparents. That sounds silly and obvious, but it is equally true for more distant ancestors. Of course, no one - even those who would consider our aunt to be our ancestor - would suggest that our most recent common ancestor would be our aunt, rather than our grandparents. That would be a useless designation.
So it seems to me that for the sake of consistency, a trait valued both by genealogists and by our research, people should choose one of two options. EITHER go back to the traditional definition of ancestors as the reverse of descendants, dropping the aunts and uncles (and the term "direct ancestor") OR start referring to your genealogical targets as MRCDA.
End of rant.