The Collaborative International Dictionary of English v.0.48:

Pailful \Pail"ful\, n.; pl. Pailfuls.
   The quantity that a pail will hold. "By pailfuls." --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pailful
    n 1: the quantity contained in a pail [syn: pail, pailful]