IPA: /ˈtiːkʌpˌfʊl/
KK: /ˈtiːkʌpˌfʊl/
The quantity of liquid that a teacup can contain.
She poured a teacupful of tea into the cup.
Teacupful is formed from "tea" (from Chinese *t'e, meaning a beverage made from the leaves of the tea plant) and "cup" (from Old English *cuppe, meaning a vessel for drinking) and "-ful" (meaning full of). The word "teacupful" refers to the amount that a teacup can hold, or full of tea.
Think of a cup that is 'full' of tea — that's what 'teacupful' means.