Definition from Wiktionary, the free dictionary
From Ancient Greek κλάδος (“shoot, branch”).
clade (plural clades)
- (biology, systematics) A group of animals or other organisms derived from a common ancestor species.
- The clade containing humans and chimps is smaller than that containing humans, chimps and fireflies
- The clade Dinosauria includes all dinosaurs as well as birds, which are descended from the dinosaurs.
- (genetics) A higher level grouping of a genetic haplogroup.
- 2004, New Scientist, 11 Sep 2004, p.13
- A clade is made up of an ancestral species and all its descendants
Derived terms 
group of animals or other organisms derived from a common ancestor species
See also 
clade m (plural cladi)
- ablative singular of clādes