The Collaborative International Dictionary of English v.0.48:

Celerity \Ce*ler"i*ty\, n. [L. celeritas, from celer swiftm
   speedy: sf. F. c['e]l['e]rit['e].]
   Rapidity of motion; quickness; swiftness.
   [1913 Webster]

         Time, with all its celerity, moves slowly to him whose
         whole employment is to watch its flight. --Johnson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

celerity
    n 1: a rate that is rapid [syn: celerity, quickness,
         rapidity, rapidness, speediness]