Definitions for "MRCA"
The ost ommon ecent ncestor between two people. For example, for two 1st cousins, their shared grandparent is the MRCA. If the cousins were both boys, they would share their grandfather's Y-chromosome.
Most Recent Common Ancestor (first abbr. I had to look up)
Most Recent Common Ancestor. The ancestor shared most recently between two individuals.
Midwest Roofing Contractors Association
Multi-Role Combat Aircraft