IPA: /ˈkreɪtfəl/
KK: /ˈkreɪtfəl/
A quantity of something that fills a crate, which is a large container used for storage or transport.
The farmer delivered a crateful of apples to the market.
Crateful is formed from "crate" (from Middle English "crate" meaning a large container) and "-ful" (meaning full of). The word "crateful" means full of crates or the amount that a crate can hold.
Think of a crate being 'full of' something — that's what crateful means.