百分百 (bǎifēnbǎi): one hundred percent

Meanings

Zhè jiàn shì wǒ bǎifēnbǎi zhīchí nǐ.

On this, I support you one hundred percent.

Tā bǎifēnbǎi shì zài shuōhuǎng.

He's absolutely lying.

usage

百分百 is a colloquial shortening of 百分之百. Both mean 100%, but 百分百 is punchier and more common in speech and ads.

百 bǎi

分 fēn