The phrase "puts one foot down" connotes taking a firm stand or making a decision. Its antonyms, or opposite meanings, include being indecisive, wavering, or vacillating. Synonyms for indecisive could be hesitant, unsure, or doubtful. To waver is to hesitate between two choices, or to be undecided, unsure, or fluctuating towards different options. Some synonyms for vacillating are oscillating, dithering, or flip-flopping. All of these antonyms stand in contrast to standing firm and taking decisive action. When one "puts one foot down," it usually means that they have resolved to take action and are committed to it, which is the opposite of being unsure or wavering.