The Collaborative International Dictionary of English v.0.48:
Cupful \Cup"ful\ (k?p"f?l), n.; pl. Cupfuls (-f?lz). As much as a cup will hold. [1913 Webster]WordNet (r) 3.0 (2006):
cupful n 1: the quantity a cup will hold; "he drank a cup of coffee"; "he borrowed a cup of sugar" [syn: cup, cupful]