Arrhenius’ definition is that states a base is any compound that donates an OH- ion to solution. Brønsted Lowry definition is for the base to accept a proton from an acid.
Potassium hydroxide is certainly a base. Any chemical substance can either be acidic (strongly or weakly), neutral, or basic (strongly or weakly). The dissociation reaction is
KOH → K+ + OH-.
Because this is a strong base
Acids are H+ (proton) donors
Bases are OH– (hydroxyl ion) donors