untimely

/ˌən-ˈtīm-lē/

adverb

  1. at an inopportune time : unseasonably

  2. before the due, natural, or proper time : prematurely

adjective

  1. inopportune, unseasonable

  2. occurring or done before the due, natural, or proper time : too early : premature

an untimely joke