Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
oi, interj., an exclamation of complaint, of one weeping: Ph. I intro nunc jam. Do. Oi! ei! Ter. Eun. 4, 4, 47: oi! hui! id. Phorm, 4, 3, 58.