ghast·ly / ˈgastlē/ • adj. (-li·er, -li·est) 1. causing great horror or fear; frightful or macabre: she was overcome with horror at the ghastly spectacle. ∎ inf. objectionable; unpleasant: we had to wear ghastly old-fashioned dresses.2. extremely unwell: he always felt ghastly first thing in the morning. ∎ deathly white or pallid: a ghastly pallor | he turned ghastly pale and rushed to the bathroom. DERIVATIVES: ghast·li·ness n.