• دَكّ
• دَكَّآء
• دَكَّة
• دُكَّتِ
• دُكَّتَا

Appears 4 times in the Quran.

1. 7:143 وَلَمَّا جَآءَ مُوسَىٰ لِمِيقَٰتِنَا وَكَلَّمَهُۥ رَبُّهُۥ قَالَ رَبِّ أَرِنِىٓ أَنظُرْ إِلَيْكَ قَالَ لَن تَرَىٰنِى وَلَٰكِنِ ٱنظُرْ إِلَى ٱلْجَبَلِ فَإِنِ ٱسْتَقَرَّ مَكَانَهُۥ فَسَوْفَ تَرَىٰنِى فَلَمَّا تَجَلَّىٰ رَبُّهُۥ لِلْجَبَلِ جَعَلَهُۥ دَكًّا وَخَرَّ مُوسَىٰ صَعِقًا فَلَمَّآ أَفَاقَ قَالَ سُبْحَٰنَكَ تُبْتُ إِلَيْكَ وَأَنَا۠ أَوَّلُ ٱلْمُؤْمِنِينَ

   And when Musa came at Our appointed time and his Lord spoke to him, he said: My Lord! show me (Thyself), so that I may look upon Thee. He said: You cannot (bear to) see Me but look at the mountain, if it remains firm in its place, then will you see Me; but when his Lord manifested His glory to the mountain He made it crumble and Musa fell down in a swoon; then when he recovered, he said: Glory be to Thee, I turn to Thee, and I am the first of the believers.
   

2. 18:98 قَالَ هَٰذَا رَحْمَةٌ مِّن رَّبِّى فَإِذَا جَآءَ وَعْدُ رَبِّى جَعَلَهُۥ دَكَّآءَ وَكَانَ وَعْدُ رَبِّى حَقًّا

   He said: This is a mercy from my Lord, but when the promise of my Lord comes to pass He will make it level with the ground, and the promise of my Lord is ever true.
   

3. 69:14 وَحُمِلَتِ ٱلْأَرْضُ وَٱلْجِبَالُ فَدُكَّتَا دَكَّةً وَٰحِدَةً

   And the earth and the mountains are borne away and crushed with a single crushing.
   

4. 89:21 كَلَّآ إِذَا دُكَّتِ ٱلْأَرْضُ دَكًّا دَكًّا

   Nay! when the earth is made to crumble to pieces,