Meaning: This sentence describes how the rainbow gradually disappeared as the clouds moved in and covered the sky, ending the beautiful display of colors.
Choice of Words: Rainbow is a noun that refers to the arc of colored light in the sky. Faded is the past tense of fade, which means to gradually lose color or intensity. As is a conjunction that means at the same time as. Clouds are masses of visible particles suspended in the atmosphere. Gathered is the past tense of gather, which means to come together in one place.