Unpredictable is a word that describes something that is unknown or unable to be foreseen. Antonyms for unpredictable include words such as reliable, consistent, dependable, certain, and trustworthy. Reliable implies a consistent track record, while consistent suggests a steadfastness in behavior or outcome. Dependable and trustworthy both denote someone or something that can be counted on to deliver as promised. Certain is used to indicate a sureness or confidence in a particular outcome. In all, these antonyms help to define what is predictable and reliable in contrast to what is subject to change or chance.