Oxford Dictionary English only child nounnoun BrE BrE//ˌəʊnli ˈtʃaɪld// ; NAmE NAmE//ˌoʊnli ˈtʃaɪld// Add to my wordlistjump to other resultsa child who has no brothers or sisters I'm an only child. Only children often relate well to adults.See only child in the Oxford Advanced American DictionaryCheck pronunciation: only child oxfordlearnersdictionaries.com