Multibillion rhymes with:
billion, billion, brazilian, castrillon, civilian, crocodilian, dillion, filion, fillion, hillian, jillion, killian, killion, mcmillian, mcmillion, million, multimillion, octillion, papillion, pavilion, pavillion, pillion, quillian, reptilian, stillion, trillion, vaudevillian, vermilion, vermillion, zillion