...Refers to the relation of different generations of descendants of
first cousins to each other.
Children of siblings (let's call them "Adam" and "Eve") would be
first cousins.
Let's call these cousins "Jane" and "John."
Jane's and John's children would be
second cousins to each other. (Let's call them Mary - Jane's child - and Tom - John's child.)
Mary's and Tom's children (Kate and Bill respectively) would be
third cousins to each other.
Each generation is one step down from original
first cousins Adam and Eve -
This is where the
removed part comes in!
Jane and John are
first cousins to each other, but are
first cousins once-removed to each other's children, Mary and Tom.
Mary and Tom are
second cousins, but are
second cousins once-removed to each other's children, Kate and Bill.
Now - Jane and John, the
first cousins, are
first cousins twice-removed to each other's grandchildren, Kate and Bill.
Now - Mary and Tom are
second cousins, but are
second cousins once-removed to each other's children, Kate and Bill.
Mary and Tom would be
second cousins twice-removed to each other's grandchildren.
Clear as mud?
These are a couple of websites that may help if I didn't

:
http://www.genealogy.com/genealogy/16_cousn.html?Welcome=1035135855http://www.janyce.com/gene/cousins.htm