English Reference
adjective · noun

undesirable

adj. · n.
US /ˌəndɪˈzaɪɹəbəɫ/ UK /ˌʌndɪzˈaɪəɹəbəl/ un·de·sir·able

  1. 01 B2 Upper Intermediate

    adj.describing something that you do not want to happen because it is bad or causes problems.

    adj.not desirable or pleasing; describing an outcome or quality that is objectionable or disadvantageous.

    Simple

    The new factory might have some undesirable effects on the local environment.

    In context

    The medication was effective at treating the primary infection, though it produced several undesirable side effects that patients found difficult to tolerate.

  2. 02 C1 Advanced Formal

    n.a person who is not wanted in a place because they are seen as trouble or low-quality.

    n.a person considered socially or morally objectionable. Often used in the plural to refer to a group of people perceived as a threat to order.

    Simple

    The hotel security tried to keep undesirables away from the private party.

    In context

    The local council was criticized for its attempts to clear the park of what it termed 'undesirables' during the international summit.

    Usage

    Usually appears in the plural form 'undesirables'.

    Teacher's tip

    This noun sense can sound quite harsh or judgmental; it is often used by authorities or in older literature to describe people they want to remove.

In part, this research gap exists because it is difficult to get accurate data on socially undesirable behaviors .

The Conversation· 3 Sept 2026

From un- + desirable.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level B2 · Upper Intermediate
Frequency Frequent
Updated