The Arabic word, Ra’d, is generally believed to be thunder, which comes from the clouds.
Once the Holy Last Messenger, peace and blessings be upon him, was asked, “Oh Messenger! What is this thunder that we hear?”
The Holy Last Messenger, peace and blessing be upon him, answered, “This thunder comes from one of the angels, from one of Allah’s many angels. Ra’d is the name of the angel that Allah has appointed to drive the clouds with a whip of lightening.”