bĭlustris, e, adj. [bis - lustrum],
that lasts two lustra, i. e. ten years , of ten years’ duration (very rare): bellum, Ov. Am. 2, 12, 9; so Sid. Carm. 23, 299.
bilūstris e, adj.bi-+lustrum, that lasts ten years : bellum, O. ...
An Elementary Latin Dictionary