Longman Dictionary of Contemporary English - mistaken

~ adj 1 someone who is mistaken is wrong about something  (be mistaken)  (I thought I saw her at the movies but I guess I was mistaken.) 2 mistaken idea/belief/impression etc a mistaken belief etc is not correct or is based on bad judgment  (Marijuana has few withdrawal effects, and this has given rise to the mistaken belief that it is not addictive.) 3 a case of mistaken identity a situation in which someone believes that they have seen a particular person taking part in a crime, when in fact it was someone else  (The police arrested her but it turned out to be a case of mistaken identity.) - mistakenly adv