The Collaborative International Dictionary of English v.0.48:
Inseparably \In*sep"a*ra*bly\, adv. In an inseparable manner or condition; so as not to be separable. --Bacon. [1913 Webster] And cleaves through life inseparably close. --Cowper. [1913 Webster]WordNet (r) 3.0 (2006):
inseparably adv 1: without possibility of separation; "these two are inseparably linked" [ant: separably]