Answer is: more H⁺ ions than OH⁻ ions.
An Arrhenius acid is a substance that dissociates in water to form hydrogen ions or protons.
For example, hydrochloric acid dissociate in aqueous solution to form hydrogen ions (H⁺) and chloride anion (Cl⁻):
HCl(aq) → H⁺(aq) + Cl⁻(aq).
An Arrhenius base is a substance that dissociates in water to form hydroxide ions (OH⁻).
For example lithium hydroxide is an Arrhenius base: LiOH(aq) → Li⁺(aq) + OH⁻(aq).