The Collaborative International Dictionary of English v.0.48:

Apace \A*pace"\, adv. [Pref. a- + pace. OE. a pas at a walk, in
   which a is the article. See Pace.]
   With a quick pace; quick; fast; speedily.
   [1913 Webster]

         His dewy locks did drop with brine apace. --Spenser.
   [1913 Webster]

         A visible triumph of the gospel draw? on apace. --I.
   Taylor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

apace
    adv 1: with rapid movements; "he works quickly" [syn: quickly,
           rapidly, speedily, chop-chop, apace] [ant:
           easy, slow, slowly, tardily]