IPA: /ˈbɒtəlfʊl/
KK: /ˈbɑtəlˌfəl/
The amount of liquid that a bottle can contain.
She poured a bottleful of water into the glass.
Bottleful → It is formed from "bottle" (from Old French *boteille*, meaning a container for liquids) and "-ful" (meaning full of). The word "bottleful" means full of a bottle or the amount that a bottle can hold.
Think of a 'bottle' as a container and '-ful' meaning full of something — so a bottleful is the amount that fills a bottle.