In the given chemical reaction, CH3COOH reacts with OH- to form CH3COO- and H2O. The compound CH3COOH is an acid because it donates a proton (H+) to the OH- ion, which accepts the proton to form H2O. As a result, CH3COO- is formed, which is the conjugate base of CH3COOH. So, the answer is "conjugate base."