integument
Concise Oxford English Dictionary © 2008 Oxford University Press:
integument /ɪnˈtɛgjʊm(ə)nt/
▶noun a tough outer protective layer, especially of an animal or plant.
– derivatives
integumental adjective,
integumentary adjective.
integumental adjective,
integumentary adjective.
– origin C17: from L. integumentum, from integere, from in- ‘in’ + tegere ‘to cover’.
'integument' also found in these Oxford entries:

