Ra-Ayn-Dal (ر-ع-د) has 1 word in the Fahm dictionary: raʿd (thunder).
In the Quran, words built on this root occur 2 times in 2 verses, across 2 of the 114 suras. The first is in 2:19. The form رَعْد (thunder) accounts for all of them.
Or like a rainstorm from the sky, wherein is darkness, thunder and the flash of lightning. They thrust their fingers in their ears by reason of the thunder-claps, for fear of death, Allah encompasseth the disbelievers (in His guidance, His omniscience and His omnipotence).
The thunder hymneth His praise and (so do) the angels for awe of Him. He launcheth the thunderbolts and smiteth with them whom He will while they dispute (in doubt) concerning Allah, and He is mighty in wrath.
Quran 13:13
Arabic text: Tanzil Quran Text (Uthmani 1.1), CC BY 3.0, tanzil.net. English: Marmaduke Pickthall, The Meaning of the Glorious Koran (1930), public domain, via Project Gutenberg. Counts and verse choice: Quranic Arabic Corpus morphology data (corpus.quran.com).