eggar Syllabification: (egg·ar)Pronunciation: /ˈegər/Definition of eggar noun a large brownish moth that is often active during the day. The caterpillars typically bear irritant hairs and make an egg-shaped cocoon. Many species in the family Lasiocampidae Origin: early 18th century: probably from egg1 + -er1eggar in other Oxford dictionaries Definition of eggar in the British & World English dictionary