From Longman Dictionary of Contemporary Englisheggcupegg‧cup /ˈeɡ-kʌp/ noun [countable] 
DFUa small container that holds a boiled egg while you eat it
DFUa small container that holds a boiled egg while you eat itExamples from the Corpus
eggcup• You could pack a ton of White Dwarf material into an eggcup.• On the upper shelf of the cupboard are four plain white plates, two plain white pudding-bowls, and another eggcup.• This time, our eggcup could contain thousands of millions of tons. 