Cumulonimbus refers to a dense, towering vertical cloud associated with thunderstorms and atmospheric instability. It's a scientific term for a powerful storm cloud.
In the song, Ateyaba uses the phrase "J'souffle un cumulonimbus" (I blow a cumulonimbus). This is a metaphorical and exaggerated way to say he's exhaling a massive amount of smoke, likely from cannabis, so much that it resembles a huge, dark storm cloud. It's an interesting and unique word choice that paints a vivid, almost fantastical image.
"Pokeball" is a brash flex track where Ateyaba boasts about the trappings of success: a hotel suite full of women, a tour bus, expensive jewelry and clothes, and money he doesn't have to share. The title comes from the line where he compares picking up women to catching a Pokémon, treating them like a prize he collects. Throughout the song he repeats that no one else is like him, framing his lifestyle and confidence as unmatched. The tone is playful and boastful rather than serious, typical of the flashy rap braggadocio style.