The Collaborative International Dictionary of English v.0.48:

Frequency \Fre"quen*cy\, n.; pl. Frequencies. [L. frequentia
   numerous attendance, multitude: cf. F. fr['e]quence. See
   Frequent.]
   1. The condition of returning frequently; occurrence often
      repeated; common occurence; as, the frequency of crimes;
      the frequency of miracles.
      [1913 Webster]

            The reasons that moved her to remove were, because
            Rome was a place of riot and luxury, her soul being
            almost stifled with, the frequencies of ladies'
            visits.                               --Fuller.
      [1913 Webster]

   2. A crowd; a throng. [Obs.] --B. Jonson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

frequency
    n 1: the number of occurrences within a given time period; "the
         frequency of modulation was 40 cycles per second"; "the
         frequency of his seizures increased as he grew older" [syn:
         frequency, frequence, oftenness]
    2: the ratio of the number of observations in a statistical
       category to the total number of observations [syn:
       frequency, relative frequency]
    3: the number of observations in a given statistical category
       [syn: frequency, absolute frequency]