From Longman Dictionary of Contemporary Englishundersellun‧der‧sell /ˌʌndəˈsel $ -ər-/ verb (past tense and past participle undersold /-ˈsəʊld $ -ˈsoʊld/) [transitive] 1 BBto sell goods at a lower price than someone else2 PERSUADEto make other people think that someone or something is less good, effective, skilful etc than they really are I think he undersold himself at the interview.→ See Verb table
Examples from the Corpus
undersell• Our prices are the lowest. We will not be undersold!• But it was Picasso who fixed the price, knowing that Modigliani would undersell himself.From Longman Business Dictionaryundersellun‧der‧sell /ˌʌndəˈsel-ər-/ verb (past tense and past participle undersold /-ˈsəʊld-ˈsoʊld/) [transitive]1COMMERCE to sell goods etc at a lower price than someone elseWe undersell all our rivals.They claim never to be undersold (=that nobody sells goods as cheaply as they do).2COMMERCE to sell something for less than its real valueWhen it was privatized, the water industry was massively undersold.3MARKETINGto make people think that a product or a person is less good, effective, skilful etc than they really areDon’t undersell yourself at the interview.→ See Verb table 