chlamydia

Concise Oxford English Dictionary © 2008 Oxford University Press:
chlamydia /kləˈmɪdɪə/

▶noun (pl. same or chlamydiae /-dɪiː/) a very small parasitic bacterium which, like a virus, requires the biochemical mechanisms of another cell in order to reproduce. [Genus Chlamydia, order Chlamydiales.]

– derivatives
chlamydial adjective.

– origin 1960s: mod. L., from Gk khlamus, khlamud- ‘cloak’.