undesirable /ˌʌndɪˈzaɪɹəbəl/adjective 1noun 1forms 3 adjective1 •Not desirable, objectionable or not likely to please.There would be no need for any of the animals to come in contact with human beings, which would clearly be most undesirable. — 1943 noun[in the plural]1 •An undesirable person.The Matchmaking Festival provided social events for these lonely-hearted pilgrims, and allowed local personages to keep undesirables away from their daughters. — 2014 formsundesirables · more undesirable · most undesirable