Definition of lo exclamation in Oxford Advanced Learner's Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. Inherited from Middle English lo, loo, from Old English lā (“exclamation of surprise, grief, or joy”). Conflated in Middle English with lo! (interjection), a corruption of lok!, loke! (“look!”) (as in lo we!(look we!)). Cognate with Scots lo, lu (“lo”). See also look. Concert events listed are based on the artist featured in the video you are watching, channels you have subscribed to, your past activity while signed in to YouTube, including artists you search. The meaning of LO is —used to call attention or to express wonder or surprise. How to use lo in a sentence. Idiom lo and behold (Definition of lo from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press) The programme made great use of time-lapse photography and of the nearest available metaphor: lo, the white blanket later became 'a white duvet'. Lo definition: Used to attract attention or to show surprise.