The Collaborative International Dictionary of English v.0.48:
Godspeed \God"speed`\ (g[o^]d"sp[=e]d`), n. Success; prosperous journeying; -- a contraction of the phrase, "God speed you." [Written also as two separate words.] [1913 Webster] Receive him not into house, neither bid him God speed. --2 John 10. [1913 Webster]WordNet (r) 3.0 (2006):
Godspeed n 1: a successful journey; "they wished him Godspeed"