IPA: //ˈpeɪl.fəl//
KK: /ˈpeɪlˌfʊl/
A quantity of something that can fill a container, specifically a pail.
He filled the pailful of water from the well.
Pailful → It is formed from "pail" (from Middle English *pail*, meaning a container for liquids) and "-ful" (meaning full of). The word "pailful" means full of a pail or the amount that a pail can hold.
Think of a 'pail' as a container that holds liquids, and '-ful' means it is full. So, a 'pailful' is simply the amount that fills a pail.