This is someone who believes that the market sometimes misprices shares and leave opportunities for anyone prepared to not follow the herd.
They look for shares that are overlooked by mainstream analysts and therefore cheap or have been pushed too high and are therefore expensive. They then do the opposite of most investors and buy unpopular stocks and dump very popular ones. It’s a potentially profitable approach for anyone with the time and the talent to attempt to “beat the market” but it can also be risky – contrarians have, for example, been calling an end to London’s property boom for the last fifteen years and missed out on some big gains in the meantime.