The Collaborative International Dictionary of English v.0.48:

busyness \busyness\ n.
   the state of being or appearing to be actively engaged in an
   activity; as, they manifested all the busyness of a pack of
   beavers.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

busyness
    n 1: the state of being or appearing to be actively engaged in
         an activity; "they manifested all the busyness of a pack of
         beavers"; "there is a constant hum of military preparation"
         [syn: busyness, hum]