The Open Dictionary

stick-in-the-mud

noun

UK/ˈstɪk.ɪn.ðəˌmʌd/
US/ˈstɪk.ɪn.ðəˌmʌd/

Definitions of stick-in-the-mud noun

  1. Countable

    A person who is considered old-fashioned, overly serious, and avoids engaging in enjoyable activities.

    • He is considered a stick-in-the-mud because he is unwilling to try new things.

    • Don't be such a stick-in-the-mud; relax and enjoy life once in a while.

    • I tried to persuade her to come to the party, but she's such a stick-in-the-mud.