بَلْ نَقْذِفُ بِالْحَقِّ عَلَى الْبَاطِلِ فَيَدْمَغُهُ فَإِذَا هُوَ زَاهِقٌ (Instead, We launch the truth against the falsehood, which smashes it, and in no time it is nothing. - 21:18) The literal meaning of قَذَف is to throw horizontally which has been translated above as launching) یدمَغُ means to hit on the head (to smash it) and زَاھِق means something which is gone or vanishes without leaving a trace.
This verse explains that Allah has not created this marvelous universe with earth and the sky for amusement. This creation is the result of a carefully thought out plan which aims at distinguishing right from wrong. Observation of Nature's creations leads people along the righteous path and protects them from evil. This idea is conveyed in the verse by saying that virtue is hurled against evil and smashes its head so completely that it disappears without a trace.