The Collaborative International Dictionary of English v.0.48:
Sempiternity \Sem`pi*ter"ni*ty\, n. [L. sempiternitas.] Future duration without end; the relation or state of being sempiternal. --Sir M. Hale. [1913 Webster]WordNet (r) 3.0 (2006):
sempiternity n 1: the property of being perpetual (seemingly ceaseless) [syn: perpetuity, sempiternity]