lapsus oculi UK /ˌlæpsəs ˈɒkjʊlaɪ/US /ˌlæpsəs ˈɑkjəˌlaɪ/ noun1 •(formal, rare) An error that results from looking in the wrong place, especially one that occurs while copying or translating a body of text.Oh, a mere lapsus oculi. The Doctor's optics were not quite so sound, as he imagined. — 1828