ب ل سb-l-s
— The bare triliteral (thulāthī mujarrad) is not in use.
Form IV (ifʿāl) أَبْلَسَ يُبْلِسُ إِبْلَاسًاablasa yublisu iblāsan: to fall silent in despair, to be struck dumb with bewilderment and hopelessness. ﴿وَيَوْمَ تَقُوْمُ السَّاعَةُ يُبْلِسُ الْمُجْرِمُوْنَ﴾ (Ar-Rūm 30:12)
مُبْلِسmublis (active participle, ism fāʿil): one whose hope is broken, dumbfounded. Five times in the Quran, each time in form ifʿāl: ﴿فَإِذَا هُمْ مُّبْلِسُوْنَ﴾ (Al-Anʿām 6:44)
إِبْلِيْسiblīs: the lexicographers derive this too from the same root (i.e. one despairing of God's mercy), though some have called it of non-Arabic origin. ﴿اِلَّآ اِبْلِيْسَ اَبٰى وَاسْتَكْبَرَ﴾ (Al-Baqarah 2:34)