Definitions

1. adjective

most changeable or unpredictable in behavior or mood; most unreliable or inconstant

“She’s considered the ficklest person in her social circle due to her frequent mood swings.”

2. adverb

in the most changeable or unpredictable way; in the most unreliable or inconstant manner

“She behaved ficklest, constantly changing her plans and disappointing her friends.”

3. noun

the most changeable or unpredictable person, thing, or situation

“The weather was the ficklest factor in their outdoor wedding plans, threatening to ruin their big day.”