fi·bro·sis \fīˈbrōsə̇s\noun (pluralfibro·ses \-ōˌsēz\) Etymology: New Latin, from fibr- + -osis : a condition marked by a relative increase in the formation of interstitial fibrous tissue in any organ or region of the body : fibrous degeneration • fi·brot·ic\(ˈ)fī|bräd.ik\adjective