勃勃 almost never stands alone - it follows a noun describing the source of vitality. The four canonical patterns:
兴致勃勃 (xìngzhì bóbó, full of zest),
野心勃勃 (yěxīn bóbó, brimming with ambition),
雄心勃勃 (xióngxīn bóbó, ambitious in a heroic sense),
生机勃勃 (shēngjī bóbó, brimming with life). The doubling of
勃 ('to rise / burst forth') intensifies the sense of bursting energy.
