The Collaborative International Dictionary of English v.0.48:
Tubful \Tub"ful\, n.; pl. Tubfuls. As much as a tub will hold; enough to fill a tub. [1913 Webster]WordNet (r) 3.0 (2006):
tubful n 1: the amount that a tub will hold; "a tub of water" [syn: tub, tubful]