What is Second Cousins?

Legal Definition
Persons who are related to each other by descending from the same great-grandfather or greatgrandmother. The children of one's first cousins are his second cousins. These are sometimes called "first cousins once removed." Slade v. Fooks, 9 Sim. 387; Corporation of Bridgnorth v. Collins, 15 Sim. 54l.
-- Black's Law Dictionary