Lewis Short
orsa (noun N) : ordior.
* Beginnings, commencements, an undertaking, attempt: ut (di) orsis tanti operis successus prosperos darent, Liv. praef. fin.: Orsa juvare,Val. Fl. 1, 21.
* In partic., words, speech (poet.): sic orsa vicissim Ore refert,Verg. A. 7, 435; 10, 632; 11, 124; Val. Fl. 5, 472: Menandri, i. e. carmina,Aus. Idyll. 4, 46.
Charlton T. Lewis, Charles Short, A Latin Dictionary