Lewis Short
(verb) : rĕ-tendo, di, tum, or sum, 3
* To release from tension, to unbend, slacken, relax (very rare; syn.: relaxo, resolvo).
* Lit.: lentos arcus,to unbend,Ov. M. 2, 419; Stat. S. 4, 4, 30; in the part. perf.: arcus retentus,Ov. M. 3, 166: arcus retensus,Phaedr. 3, 14, 5.— *
* Trop.: ea quoque, quae sensu et animā carent, velut alternā quiete retenduntur, i. e. unbend, relax (shortly before, remissio), Quint. 1, 3, 8.
Charlton T. Lewis, Charles Short, A Latin Dictionary